LaTeX writer: fix text style in math mode and strikethrough

[engeir]

I believe this wasn't fully fixed with the linked commit b28dc15 in issue #9597. Some further examples that both result in the same soul error as described in the issue: (on pandoc 3.1.13)

[$T$]{.underline}
[$T$]{.mark}

Further,

~~SO~2~~~

results in (that said, ~~$\mathrm{SO_2}$~~ works, so this is maybe not an issue?)

Error producing PDF.
! Argument of \textsubscript  has an extra }.
<inserted text>
                \par
l.64 \st{SO\textsubscript{2}}

[jgm]

OK, I think I have a more general fix.
(I don't know what to do about the last example, but I'm not going to worry about it because you can use math mode.)

[jgm]

Closed by 91e7585