Remove setuptools-scm-git-archive, require setuptools-scm>=7

[mwtoews]

Since June 2022, setuptools_scm_git_archive is obsolete since "setuptools_scm >= 7.0.0 supports Git archives by itself".

This PR follows the migration guide to update .git_archival.txt, and establish setuptools-scm>=7 in pyproject.toml.

[keewis]

thanks for the PR, @mwtoews! I noticed that a few hours ago (probably just after you opened this PR) the documentation of setuptools_scm was changed to recommend

describe-name: $Format:%(describe:tags=true,match=*[0-9]*)$

instead of

describe-name: $Format:%(describe:tags=true)$

Should we also be using that? Or would that require a development version of setuptools_scm?

[mwtoews]

I've looked into this further, and what I see is that $Format:%(describe:tags=true)$ requires git 2.35.0 (January 2022) or later; see docs here. Earlier versions will just leave "%(describe:tags=true)" without substitution or error. I presume "git archive" would be running on newish GitHub actions versions of git.

As for the updated format with a numeric match, I don't think it makes any difference. Testing with git 2.38.1:

$ git log -2 --format="%(describe:tags=true,match=*[0-9]*)"
v2022.10.0-47-g2e6fab2f
v2022.10.0-46-g6179d8e8
$ git log -2 --format="%(describe:tags=true)"
v2022.10.0-47-g2e6fab2f
v2022.10.0-46-g6179d8e8

but I've amended this PR with the new change to keep it aligned with the latest docs.

[keewis]

sorry, this dropped off my radar.

Looks good to me (and a quick test with git archive demonstrates that it does work), so I suggest we merge after CI is green