Add AR6 category colors to PYAM_COLORS

[jkikstra]

Description of PR

Adds the AR6 Category and IMP colours to pyam.

[gidden]

Thanks so much, @jkikstra! Can you also update the plot used to test against (and confirm it looks correct)? Instructions to do so should be in the test folder and can be executed on the single file/test of interest.

[jkikstra]

Have updated the test figures.
As expected, only https://github.com/IAMconsortium/pyam/blob/56fcc56f6f38fdd9f089074379babbfb33c9a476/tests/expected_figs/test_line_PYAM_COLORS.png changed.

Tests locally are failing, but that seems to be due to pint and/or pandas_datareader, so should not really part of this PR.

[danielhuppmann]

Thanks @jarmo! I pinned pint as a quickfix, this should resolve the failing unit tests in this PR.

Could you please do the following:

• Revert the latest commit and then commit only the one changed figure to this branch
• Add a comment in each line explaining the meaning of the abbreviations and a reference to the description or source in the AR6 WG3 report, so that users have a chance to know what "C2" or "IMP-Neg" are...
• Add a line to the release notes

Then good to go, and I think this is a nice feature addition that warrants a new release (which I will take of).

[codecov]

Codecov Report

Merging #650 (b82fe83) into main (fff690e) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##            main    #650   +/-   ##
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  Coverage   94.5%   94.5%           
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  Files         57      57           
  Lines       5662    5662           
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  Hits        5356    5356           
  Misses       306     306           

Impacted Files	Coverage Δ
pyam/plotting.py	92.9% <ø> (ø)

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[jkikstra]

Hi Daniel and Matt, thanks for the guidance.

I did that now.

Tried to also update the python notebook that is part of the docs, ipcc_colors.ipynb, but my IIASA desktop seems unhappy due to some dll issue in my venv, so would probably be more efficient if I leave that quick update to you.

[danielhuppmann]

Thanks @jkikstra for adding the colors and docs!

The IPCC-colors tutorial notebook is run automatically as part of building the docs, so this will show the added AR6 colors. No need to change anything explicitly.