[8.0] test: extra_module default to empty list

[chaen]

Typer 0.10.0 fixed the behavior of list|None paramaters which default to None.
https://typer.tiangolo.com/release-notes/#fixes
fastapi/typer#664

Without this fix, our integration tests fail with

Traceback (most recent call last):

  File "/tmp/DIRACRepo/./integration_tests.py", line 1[15](https://github.com/DIRACGrid/diracx/actions/runs/8410072574/job/23028073455?pr=225#step:6:16)4, in <module>
    app()

  File "/tmp/DIRACRepo/./integration_tests.py", line 208, in prepare_environment
    modules = DEFAULT_MODULES | dict(f.split("=", 1) for f in extra_module)
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

BEGINRELEASENOTES

*Test
FIX: extra_module default to empty list
ENDRELEASENOTES

[DIRACGridBot]

Sweep summary

Sweep ran in https://github.com/DIRACGrid/DIRAC/actions/runs/8414188338

Failed:

• integration
  cherry-pick ef7d337 into integration failed
  check merge conflicts on a local copy of this repository

  git fetch upstream
  git checkout upstream/integration -b cherry-pick-2-ef7d33751-integration
  git cherry-pick -x -m 1 ef7d33751
  # Fix the conflicts
  git cherry-pick --continue
  git commit --amend -m 'sweep: #7537 test: extra_module default to empty list' --author='Christophe Haen <[email protected]>'
  git push -u origin cherry-pick-2-ef7d33751-integration
  
  # If you have the GitHub CLI installed the PR can be made with
  gh pr create \
       --label 'sweep:from rel-v8r0' \
       --base integration \
       --repo DIRACGrid/DIRAC \
       --title '[sweep:integration] test: extra_module default to empty list' \
       --body 'Sweep #7537 `test: extra_module default to empty list` to `integration`.
  
  Adding original author @chaen as watcher.
  
  BEGINRELEASENOTES
  
  *Test
  FIX: extra_module default to empty list
  ENDRELEASENOTES
  Closes #7538'