chore: keep the backport marker out of the release notes (#32392)

.github/workflows/command-backport.yml

@@ -162,11 +162,13 @@ jobs:
 
           # the pull request is authored by the deploy token, so assign the
           # requester. the body stays empty, squashing it would carry the text
-          # into the release branch as the commit description
+          # into the release branch as the commit description.
+          # the marker trails the title so the changelog filters and groups still
+          # see the original prefix, goreleaser strips it from the release notes
           url=$(gh pr create \
             --base "$TARGET" \
             --head "$BRANCH" \
-            --title "$line backport: $TITLE" \
+            --title "$TITLE [$line backport]" \
             --label backport \
             --assignee "$ACTOR" \
             --body "")

.goreleaser.yml

@@ -67,6 +67,8 @@ snapshot:
 
 changelog:
   sort: asc
+  # drop the marker the backport command appends to the pull request title
+  format: '{{ .SHA }} {{ reReplaceAll ` \[\d+\.\d+ backport\]` .Message "" }}'
   filters:
     exclude:
       - "^chore"