Use sha instead event payload (#18897)

Author: Kordyjan

.github/workflows/lts-backport.yaml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   add-to-backporting-project:
-    if: "!contains(github.event.push.message, '[Next only]')"
+    if: "!contains(github.event.push.head_commit.message, '[Next only]')"
     runs-on: ubuntu-latest
 
     steps:
@@ -16,7 +16,7 @@ jobs:
           fetch-depth: 0
       - uses: coursier/cache-action@v6
       - uses: VirtusLab/scala-cli-setup@v1.0.5
-      - run: scala-cli ./project/scripts/addToBackportingProject.scala -- ${{ github.event.push.after }}
+      - run: scala-cli ./project/scripts/addToBackportingProject.scala -- ${{ github.sha }}
         env:
           GRAPHQL_API_TOKEN: ${{ secrets.GRAPHQL_API_TOKEN }}