Merge PR #6502: MAINT(ci): Don't run backport action on backport PRs

Author: Krzmbrzl

.github/workflows/backport.yml

@@ -7,7 +7,7 @@ on:
 jobs:
   backport:
     name: Backport PR
-    if: github.event.pull_request.merged == true
+    if: github.event.pull_request.merged == true && !(contains(github.event.pull_request.labels.*.name, 'backport'))
     runs-on: ubuntu-latest
     steps:
       - name: Backport Action