Cosmo latex identify and cleanup - #15088

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The only question I have is that I couldn't find any rendered version of the updated write_latex docstring in the docs to review.

Yeah, the cosmology I/O docs need some work. This is being done in #15090.

Also, in the cosmology Read, Write ... section, there is no place that ascii.latex is explicitly mentioned so it isn't clear how the user will discover format="ascii.latex".

It should be in the list of write formats in the I/O table... If not #15090 will take of that!

Thanks @taldcroft for the reviews!