Revert "Stop using String token in pygments lexers"

[denismerigoux]

Reverts #772 : the fix completely breaks at least the generation of the Catala syntax sheet cheat (see attached) :

[denismerigoux]

@pierregoutagny I'm sorry your fix was not the right solution it seems...

[denismerigoux]

Instead, the syntax sheet cheat was correctly generated before the #772 PR was merged (https://github.com/CatalaLang/catala/actions/runs/12745997886) :

[pierregoutagny]

Oh sorry for this break. I have trouble compiling the syntax.pdf file locally (it looks like your screenshot no matter the version), but my guess would be that if you do the same as for the unit test it could work. For instance, could you check if the pdf works when you remove the \PYG on lines 201 and 202 of syntax_en.tex ? That is replacing

\newcommand*\FancyVerbStartString{\PYG{l+s}{```catala}}
\newcommand*\FancyVerbStopString{\PYG{l+s}{```}}

by

\newcommand*\FancyVerbStartString{```catala}
\newcommand*\FancyVerbStopString{```}

[denismerigoux]

Oh yes replacing \PYG{l+s}{```catala}} by {```catala} is probably a good fix. Can you put it in another PR? I'll merge this new one and hope it fixes the cheat sheet.