rc markdown: Fix code fence regex

The invalid regex `)\b` currently matches anything, so this didn't cause
any errors.
It is still invalid though, so I fixed it by moving the `\b` to the end
of the non-raw_attribute language name (like the original regex). The
raw_attribute one shouldn't need this because the `}` marks the end of
the language name anyway.

Fixes #4025

0 files changed, 0 insertions, 0 deletions