Ignore __init__.py in snippets.toml (#9272)

Adding that `__init__.py` in #9260 made mypy happy but snippets sad.
It's now explicitly ignored.

Author: abey79

docs/snippets/snippets.toml

@@ -76,6 +76,7 @@ features = [
 # You should only ever use this if the test isn't implemented and cannot yet be implemented
 # for one or more specific SDKs.
 [opt_out.run]
+"__init__" = ["py"] # That init file is to make mypy happy.
 "concepts/explicit_recording" = [ # python-specific check
   "cpp",
   "rust",