Incorrect `--show-source` for Jupyter Notebooks with continuous import blocks

[dhruvmanila]

Take the test case as an example where there are two cells with unsorted imports.

When run using the following command:

cargo run --bin ruff -- check --select=I001 --no-cache --isolated crates/ruff/resources/test/fixtures/jupyter/isort.ipynb --show-source

The output is a single diagnostic:

crates/ruff/resources/test/fixtures/jupyter/isort.ipynb:cell 1:1:1: I001 [*] Import block is un-sorted or un-formatted
  |
1 | / from pathlib import Path
2 | | import random
3 | | import math
4 | | from typing import Any
5 | | import collections
6 | | # Newline should be added here
  | |_^ I001
7 |   def foo():
8 |       pass
  |
  = help: Organize imports

Found 1 error.
[*] 1 potentially fixable with the --fix option.

While there are 2 import blocks (separated by a cell boundary). The fix produces the correct number which is 2:

$ cargo run --bin ruff -- check --select=I001 --no-cache --isolated crates/ruff/resources/test/fixtures/jupyter/isort.ipynb --fix       
    Finished dev [unoptimized + debuginfo] target(s) in 0.38s
     Running `target/debug/ruff check --select=I001 --no-cache --isolated crates/ruff/resources/test/fixtures/jupyter/isort.ipynb --fix`
Found 2 errors (2 fixed, 0 remaining).

[dhruvmanila]

Oh, I think I found the problem. Should be an easy fix actually :)