CI: Disallow spaces just before the separating colon in commit titles

Meta/lint-commit.sh

@@ -23,7 +23,7 @@ while read -r line; do
   ((line_number += 1))
   line_length=${#line}
 
-  category_pattern="^\S.*?: .+"
+  category_pattern="^\S.*?\S: .+"
   if [[ $line_number -eq 1 ]] && (echo "$line" | grep -P -v -q "$category_pattern"); then
     error "Missing category in commit title (if this is a fix up of a previous commit, it should be squashed)"
   fi