github: workflows: no_not_merge: Fix set of checked labels

Also consider "DNM (manifest)" for this workflow.

Signed-off-by: Johan Hedberg <johan.hedberg@silabs.com>

Author: jhedberg

.github/workflows/do_not_merge.yml

@@ -9,12 +9,13 @@ on:
 
 jobs:
   do-not-merge:
-    if: ${{ contains(github.event.*.labels.*.name, 'DNM') }}
+    if: ${{ contains(github.event.*.labels.*.name, 'DNM') ||
+            contains(github.event.*.labels.*.name, 'DNM (manifest)') }}
     name: Prevent Merging
     runs-on: ubuntu-24.04
     steps:
       - name: Check for label
         run: |
-          echo "Pull request is labeled as 'DNM'."
+          echo "Pull request is labeled as 'DNM' or 'DNM (manifest)'."
           echo "This workflow fails so that the pull request cannot be merged."
           exit 1