Use Sequence[] instead of list[] for lists of StrPath

[felixfontein]

Follow-up to #105, which broke type checks for antsibull:

src/antsibull/build_ansible_commands.py:656: error: Argument 1 to "install_together" has incompatible type "list[str]"; expected "list[str | PathLike[str]]"  [arg-type]
src/antsibull/build_ansible_commands.py:656: note: "List" is invariant -- see https://mypy.readthedocs.io/en/stable/common_issues.html#variance
src/antsibull/build_ansible_commands.py:656: note: Consider using "Sequence" instead, which is covariant

(https://github.com/ansible-community/antsibull/actions/runs/6766190684/job/18386917570)

[felixfontein]

@gotmax23 thanks a lot for reviewing and merging!