ci: Modify workflow to add no changelog label

Author: jorisv

.github/workflows/update_pixi_lockfile.yml

@@ -45,6 +45,8 @@ jobs:
           body-path: diff.md
           branch: topic/update-pixi
           base: devel
-          labels: pixi
+          labels: |
+            pixi
+            no changelog
           delete-branch: true
           add-paths: pixi.lock