[pylint] Stabilize len-test (PLC1802)

[ntBre]

Summary

Stabilizes PLC1802. The tests were already in the right place, and I just tidied the docs a little bit.

Test Plan

1 issue closed 4 days after the rule was added, no other issues

[github-actions]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check detected linter changes. (+29 -0 violations, +0 -0 fixes in 6 projects; 49 projects unchanged)

apache/airflow (+7 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --no-preview --select ALL

+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1743:8: PLC1802 [*] `len(success_entries)` used as condition without comparison
+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1750:8: PLC1802 [*] `len(skipped_entries)` used as condition without comparison
+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1855:12: PLC1802 [*] `len(success_entries)` used as condition without comparison
+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1862:12: PLC1802 [*] `len(skipped_entries)` used as condition without comparison
+ providers/amazon/src/airflow/providers/amazon/aws/hooks/glue.py:268:16: PLC1802 [*] `len(fetched_logs)` used as condition without comparison
+ providers/sftp/src/airflow/providers/sftp/sensors/sftp.py:132:16: PLC1802 [*] `len(files_found)` used as condition without comparison
+ providers/snowflake/src/airflow/providers/snowflake/operators/snowflake.py:474:20: PLC1802 [*] `len(queries_in_progress)` used as condition without comparison

apache/superset (+5 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --no-preview --select ALL

+ superset/databases/filters.py:98:16: PLC1802 [*] `len(allowed_schemas)` used as condition without comparison
+ superset/migrations/versions/2018-07-22_11-59_bebcf3fed1fe_convert_dashboard_v1_positions.py:444:61: PLC1802 [*] `len(SEQUENCE)` used as condition without comparison
+ superset/migrations/versions/2018-07-22_11-59_bebcf3fed1fe_convert_dashboard_v1_positions.py:546:11: PLC1802 [*] `len(ordered_raw_positions)` used as condition without comparison
+ superset/migrations/versions/2018-07-22_11-59_bebcf3fed1fe_convert_dashboard_v1_positions.py:559:16: PLC1802 [*] `len(available_columns_index)` used as condition without comparison
+ superset/migrations/versions/2018-11-12_13-31_4ce8df208545_migrate_time_range_for_default_filters.py:68:24: PLC1802 [*] `len(keys)` used as condition without comparison

bokeh/bokeh (+1 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --no-preview --select ALL

+ src/bokeh/core/validation/check.py:216:27: PLC1802 [*] `len(warnings)` used as condition without comparison

pandas-dev/pandas (+10 -0 violations, +0 -0 fixes)

+ pandas/core/arrays/string_arrow.py:284:16: PLC1802 [*] `len(value_set)` used as condition without comparison
+ pandas/core/groupby/generic.py:2508:16: PLC1802 [*] `len(results)` used as condition without comparison
+ pandas/core/groupby/groupby.py:5177:16: PLC1802 [*] `len(to_coerce)` used as condition without comparison
+ pandas/core/internals/blocks.py:811:16: PLC1802 [*] `len(pairs)` used as condition without comparison
+ pandas/core/internals/construction.py:867:8: PLC1802 [*] `len(contents)` used as condition without comparison
+ pandas/core/internals/managers.py:1301:12: PLC1802 [*] `len(removed_blknos)` used as condition without comparison
+ pandas/io/pytables.py:1763:16: PLC1802 [*] `len(lkeys)` used as condition without comparison
+ pandas/io/pytables.py:4543:12: PLC1802 [*] `len(masks)` used as condition without comparison
+ pandas/io/pytables.py:4663:20: PLC1802 [*] `len(groups)` used as condition without comparison
+ pandas/io/sql.py:2618:12: PLC1802 [*] `len(ix_cols)` used as condition without comparison

pytest-dev/pytest (+1 -0 violations, +0 -0 fixes)

+ testing/_py/test_local.py:218:16: PLC1802 [*] `len(lst)` used as condition without comparison

astropy/astropy (+5 -0 violations, +0 -0 fixes)

+ astropy/io/ascii/misc.py:83:12: PLC1802 [*] `len(first)` used as condition without comparison
+ astropy/units/core.py:1331:16: PLC1802 [*] `len(subresults)` used as condition without comparison
+ astropy/units/core.py:2549:12: PLC1802 [*] `len(names)` used as condition without comparison
+ astropy/wcs/wcs.py:2950:16: PLC1802 [*] `len(missing_keys)` used as condition without comparison
+ astropy/wcs/wcs.py:3765:20: PLC1802 [*] `len(content)` used as condition without comparison

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
PLC1802	29	29	0	0	0

Linter (preview)

✅ ecosystem check detected no linter changes.

[ntBre]

The ecosystem results look right to me. I checked that they were all len(...) calls and also that the ... was a sequence. There was one case where it wasn't obvious to me that it was a sequence, but it looks like the simple type inference looked at the class definition with an annotation and got it right.