Check notebook syntax in pre-commit hooks

I just realised we're effectively skipping the notebooks AST check because nbQA excludes cells with syntax errors by default.

I've made a deliberate bad commit here to ensure that the check can pick it up now. I'll cut that out before merging.

Yes, it fails:

nbqa-check-ast...........................................................Failed
- hook id: nbqa-check-ast
- exit code: 1
notebooks/LPDMini/LPD_Mini_Correct.ipynb: failed parsing with CPython 3.11.10:
    Traceback (most recent call last):
      File "/root/.cache/pre-commit/repokgn9cdot/py_env-python3/lib/python3.11/site-packages/pre_commit_hooks/check_ast.py", line 21, in main
        ast.parse(f.read(), filename=filename)
      File "/usr/local/lib/python3.11/ast.py", line 50, in parse
        return compile(source, filename, mode, flags,
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "notebooks/LPDMini/LPD_Mini_Correct.ipynb", line 3
        in_folder = "/gpfs/exfel/exp/FXE/202321/p004576/raw/  # the folder to read data from, required
                    ^
    SyntaxError: unterminated string literal (detected at line 3)

https://git.xfel.eu/calibration/pycalibration/-/jobs/754201

Nice, this is really useful. Imagine someone would accidently add a character just in between testing and git commit, and then deploy during operations.

marked this merge request as ready

I've removed the bad commit again, and the pre-commit checks are passing (although they only run on the files changed in the MR, which is now no notebooks)

merged

mentioned in commit 8576143a

changed milestone to %3.15.5