[ci] Fix torch dependency issue and pause tests on Mac/Python3.8

[ebezzi]

1. Pins torch to 2.2.x, as 2.3.x is causing dependency issues (these will eventually be fixed, so we should periodically retry unpinning the dependency)
2. Pause python 3.8 tests on the MacOS runner, at least temporarily. This is an issue with gfortran - maybe something like https://github.com/actions/runner-images/issues/3371 could help with solving the issue.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.12%. Comparing base (a7b0bf7) to head (280e495). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1118 +/- ## ======================================= Coverage 91.12% 91.12% ======================================= Files 77 77 Lines 5857 5857 ======================================= Hits 5337 5337 Misses 520 520 ``` | [Flag](https://app.codecov.io/gh/chanzuckerberg/cellxgene-census/pull/1118/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/chanzuckerberg/cellxgene-census/pull/1118/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg) | `91.12% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg#carryforward-flags-in-the-pull-request-comment) to find out more.

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