Limit scipy to version before 1.12 which introduces a breaking change and unfreeze sphinx version

[gabemery]

The breaking change I encountered is fixed in gammapy main branch but not in a release yet.

Error during lstchain tests with the latest scipy :

../../../micromamba-root/envs/lst-dev/lib/python3.10/site-packages/gammapy/utils/roots.py:9: in <module>
    BAD_RES = RootResults(root=np.nan, iterations=0, function_calls=0, flag=0)
E   TypeError: RootResults.__init__() missing 1 required positional argument: 'method'

'method' is introduced in scipy 1.12.0

EDIT Daniel Morcuende: I unfreeze the version of sphinx that was being used (~4) because it was giving problems in the docs building:

Sphinx version error:
The sphinxcontrib.applehelp extension used by this project needs at least Sphinx v5.0; it therefore cannot be built with this version.

[codecov[bot]]

Codecov Report

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

Comparison is base (089891d) 74.22% compared to head (acce0df) 74.22%.

:exclamation: Current head acce0df differs from pull request most recent head 5811da6. Consider uploading reports for the commit 5811da6 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1201 +/- ## ======================================= Coverage 74.22% 74.22% ======================================= Files 130 130 Lines 13279 13279 ======================================= Hits 9857 9857 Misses 3422 3422 ```

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