This new section didn't use the correct RST syntax, and ended up
with a broken section in the rendered docs.
Fix the syntax, and clean things up a bit to avoid overly long lines.
Fixes: be235edfe2 ("zink: add profile documentation")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19481>
(cherry picked from commit 6b3b633391)