Pin pytest to fix CI

[mraspaud]

This PR limits pytest to <8.0 to fix the CI

[codecov[bot]]

Codecov Report

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

Comparison is base (57122d3) 95.40% compared to head (0c10810) 95.40%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2730 +/- ## ======================================= Coverage 95.40% 95.40% ======================================= Files 371 371 Lines 52825 52825 ======================================= Hits 50399 50399 Misses 2426 2426 ``` | [Flag](https://app.codecov.io/gh/pytroll/satpy/pull/2730/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | Coverage Δ | | |---|---|---| | [behaviourtests](https://app.codecov.io/gh/pytroll/satpy/pull/2730/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `4.15% <ø> (ø)` | | | [unittests](https://app.codecov.io/gh/pytroll/satpy/pull/2730/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `96.02% <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=pytroll#carryforward-flags-in-the-pull-request-comment) to find out more.

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[coveralls]

Pull Request Test Coverage Report for Build 7697525358

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.968%

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Totals
Change from base Build 7670481337:	0.0%
Covered Lines:	50525
Relevant Lines:	52648

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💛 - Coveralls