ci: update old backport.yml

Update to use zephyr fork of backport.

Signed-off-by: Kari Hamalainen <[email protected]>

.github/workflows/backport.yml

@@ -1,19 +1,29 @@
 name: Backport
 on:
-  pull_request:
+  pull_request_target:
     types:
       - closed
       - labeled
+    branches:
+      - main
 
 jobs:
   backport:
-    runs-on: ubuntu-20.04
     name: Backport
+    runs-on: ubuntu-22.04
+    # Only react to merged PRs for security reasons.
+    # See https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target.
+    if: >
+      github.event.pull_request.merged &&
+      (
+        github.event.action == 'closed' ||
+        (
+          github.event.action == 'labeled' &&
+          contains(github.event.label.name, 'backport')
+        )
+      )
     steps:
-      - name: Backport Bot
-        uses: Gaurav0/backport@v1.0.24
+      - name: Backport
+        uses: zephyrproject-rtos/action-backport@v2.0.3-3
         with:
-          bot_username: NordicBuilder
-          bot_token: 151a9b45052f9ee8be5a59963d31ad7b92c3ecb5
-          bot_token_key: 67bb1f1f998d546859786a4088917c65415c0ebd
           github_token: ${{ secrets.GITHUB_TOKEN }}