Harmonize GitHub Actions structure

See https://github.com/spring-projects/spring-boot/issues/42512

.github/workflows/backport-bot.yml

@@ -1,5 +1,4 @@
 name: Backport Bot
-
 on:
   issues:
     types: [labeled]
@@ -29,6 +28,6 @@ jobs:
         run: wget https://github.com/spring-io/backport-bot/releases/download/latest/backport-bot-0.0.1-SNAPSHOT.jar
       - name: Backport
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           GITHUB_EVENT: ${{ toJSON(github.event) }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: java -jar backport-bot-0.0.1-SNAPSHOT.jar --github.accessToken="$GITHUB_TOKEN" --github.event_name "$GITHUB_EVENT_NAME" --github.event "$GITHUB_EVENT"