compat: altair 5.5.0

[hoxbro]

In my opinion, it isn't worth keeping a compatibility layer with try/except for docstring, so I updated it to the newest API.

[MarcSkovMadsen]

There is also a couple of places in the docs to fix:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.54%. Comparing base (1f821d6) to head (19f5177).

❗ There is a different number of reports uploaded between BASE (1f821d6) and HEAD (19f5177). Click for more details.

HEAD has 8 uploads less than BASE

Flag	BASE (1f821d6)	HEAD (19f5177)
	12	4

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #7523       +/-   ##
===========================================
- Coverage   82.38%   41.54%   -40.84%     
===========================================
  Files         339      327       -12     
  Lines       50995    48679     -2316     
===========================================
- Hits        42010    20225    -21785     
- Misses       8985    28454    +19469     

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