Sync web-platform-tests PR 22839 into mozilla-central (this bug is closed when the sync is complete).

PR: https://github.com/web-platform-tests/wpt/pull/22839
Details from upstream follow.

pyup-bot <github-bot@pyup.io> wrote:

Update pyflakes to 2.2.0

This PR updates pyflakes from 2.1.1 to 2.2.0.

<details>
<summary>Changelog</summary>

### 2.2.0
```
- Include column information in error messages

• Fix overload detection with other decorators and in non-global scopes
• Fix return-type annotation being a class member
• Fix assignment to _ in doctests with existing _ name
• Namespace attributes which are attached to ast nodes with _pyflakes_ to
  avoid conflicts with other libraries (notably bandit)
• Add check for f-strings without placeholders
• Add check for unused/extra/invalid 'string literal'.format(...)
• Add check for unused/extra/invalid 'string literal % ...
• Improve python shebang detection
• Allow type ignore to be followed by a code type: ignore[attr-defined]
• Add support for assignment expressions (PEP 572)
• Support overload detection from typing_extensions as well
• Fix overload detection for async functions
• Allow continue inside finally in python 3.8+
• Fix handling of annotations in positional-only arguments
• Make pyflakes more resistant to future syntax additions
• Fix false positives in partially quoted type annotations
• Warn about is comparison to tuples
• Fix Checker usage with async function subtrees
• Add check for if of non-empty tuple
• Switch from optparse to argparse
• Fix false positives in partially quoted type annotations in unusual contexts
• Be more cautious when identifying Literal type expressions

</details>

<details>
<summary>Links</summary>

• PyPI: https://pypi.org/project/pyflakes
• Changelog: https://pyup.io/changelogs/pyflakes/
• Repo: https://github.com/PyCQA/pyflakes
  </details>

https://hg.mozilla.org/mozilla-central/rev/dd3c8152b769