[pre-commit] add 'tomli' dependency for codespell pre-commit hook

The codespell pre-commit hook imports the 'tomllib' module to parse
'pyproject.toml'.  'tomllib' is not available for Python versions 3.10
and older.  Add a dependency on 'tomli' so the hook also works on these
Python versions.

Approved-By: Tom de Vries <tdevries@suse.de>