Fixes https://github.com/go-gitea/gitea/issues/39770
`\(x^2\)is` and `\(x^2\)123` rendered as plain text because `\(...\)`
went through the same check on surrounding characters as `$...$`. That
check is there to skip things like `US$1`, which can't happen with
explicit `\(` `\)` delimiters, so it's now skipped for them, the same as
for "$`...`$". `$x$a` still isn't parsed.
Yunus Ozen
41ccfce3e9