Fix colab and pybtex issue

[Saransh-cpp]

Description

This looks like this right now -

Now that I think of it, it might be better to not show a warning on importing pybamm (would be too noisy). Rather, we could do -

    def __init__(self):
        # Set of citation keys that have been registered
        self._papers_to_cite = set()

        # Dict mapping citations keys to BibTex entries
        self._all_citations: dict[str, str] = dict()

        if "google.colab" not in sys.modules:
            self.read_citations()
            self._reset()

and then -

def print_citations(filename=None, output_format="text"):
    """See :meth:`Citations.print`"""
    if "google.colab" in sys.modules:
        warnings.warn(
            """pybtex does not work with Google Colab due to a known bug -
            https://bitbucket.org/pybtex-devs/pybtex/issues/148/.
            Please manually cite all the references.""".replace(
                "\n                ", " "
            ),
        )
    else:
        pybamm.citations.print(filename, output_format)

Fixes #2524

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ flake8
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

Base: 99.72% // Head: 99.72% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (3377175) compared to base (57fe822).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2526   +/-   ##
========================================
  Coverage    99.72%   99.72%           
========================================
  Files          268      268           
  Lines        19311    19315    +4     
========================================
+ Hits         19258    19262    +4     
  Misses          53       53           

Impacted Files	Coverage Δ
pybamm/citations.py	100.00% <100.00%> (ø)

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[valentinsulzer]

Looks good thanks! Will merge when tests pass

[valentinsulzer]

cool test!

[Saransh-cpp]

😄