chore(release-drafter): wrap pull-request reference in square bracket

- easier conversion to news post

Author: curbengh

.github/release-drafter.yml

@@ -21,7 +21,7 @@ categories:
   - title: 'Refactor'
     labels:
       - 'refactor'
-change-template: '- $TITLE @$AUTHOR (#$NUMBER)'
+change-template: '- $TITLE @$AUTHOR [#$NUMBER]'
 template: |
   ## Changes