Include - in allowed characters for bibtex references

[alistairsellar]

Description

Very small change that correctly handles bibtex references that include -, as is the case for many bibtex files in esmvaltool/references.
Closes #2092
Required to fix warnings arising from ESMValGroup/ESMValTool#3197 (comment)

Link to documentation: https://esmvaltool--2097.org.readthedocs.build/projects/ESMValCore/en/2097/ (no change)

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[codecov]

Codecov Report

Merging #2097 (85a1892) into main (179312e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2097   +/-   ##
=======================================
  Coverage   93.08%   93.08%           
=======================================
  Files         237      237           
  Lines       12793    12793           
=======================================
  Hits        11909    11909           
  Misses        884      884           

Impacted Files	Coverage Δ
esmvalcore/_citation.py	80.99% <100.00%> (ø)

[alistairsellar]

Hi @bouweandela here is the PR for the parsing bug #2092. Please could you review?

I've marked as 2.9 but appreciate the Core deadline for that has passed, so understand if it gets bumped to 2.10.

[bouweandela]

Thanks @alistairsellar! I've added a unit test for you. It looks like there were no unit tests for the module yet, so I started it in a new file.

[bouweandela]

@ESMValGroup/technical-lead-development-team Could someone please do a final check and merge?

[alistairsellar]

Thanks @alistairsellar! I've added a unit test for you. It looks like there were no unit tests for the module yet, so I started it in a new file.

Thanks @bouweandela! Nice to see how a unit test can be added for such a simple change - this had not occurred to me as something that was even applicable for this change, but of course it is.

[alistairsellar]

Thanks @schlunma and @bouweandela!