Fix Ruff test-bad-syntax exclusion

[MichaReiser]

This PR fixes ruff check . which started failing with after moving the exclude to [ruff.lint]

ruff failed
  Cause: TOML parse error at line 2, column 19
  |
2 | requires = ['bad' 'syntax']
  |                   ^
invalid array
expected `]`

ruff.exclude and ruff.lint.exclude have slightly different semantics:

• ruff.exclude: Excludes files from your project, so that ruff skips them for all commands. This also prevents ruff from loading configuration files in excluded directories.
• ruff.lint.exclude: Excludes files from linting only. However, ruff loads the files (and related configurations).

You want ruff.lint.exclude to avoid the intentionally malformed configuration.

Question: Could we improve our documentation to make this distinction more clear?

Test Plan

ruff check . no longer fails because of the malformed configuration.