bin/gen_release_notes: escape at-symbols

If we don't do this, we end up with email-alike strings to be turned
into mailto links. This is not what we want.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25712>

bin/gen_release_notes.py

@@ -168,6 +168,7 @@ class Inliner(states.Inliner):
                 break
         # Quote all original backslashes
         checked = re.sub('\x00', "\\\x00", checked)
+        checked = re.sub('@', '\\@', checked)
         return docutils.utils.unescape(checked, 1)
 
 inliner = Inliner();