pyproject.toml: Add ruff.lint prefixes to format settings.

[Josverl]

ruff ruff 0.11.6 is warming about the settings.

 ruff format 
warning: The top-level linter settings are deprecated in favour of their counterparts in the `lint` section. Please update the following options in `pyproject.toml`:
  - 'ignore' -> 'lint.ignore'
  - 'select' -> 'lint.select'
  - 'mccabe' -> 'lint.mccabe'
  - 'pylint' -> 'lint.pylint'
  - 'per-file-ignores' -> 'lint.per-file-ignores'

[dpgeorge]

Instead of this and the change below, maybe change the heading on line 1 to [tool.ruff.lint]? That matches the main MicroPython repo's settings.

[dpgeorge]

Following the main MicroPython repo, this could move into the above section as:

mccabe.max-complexity = 40