Update workflow to use App Auth

Signed-off-by: Matty Widdop <18513864+MattyTheHacker@users.noreply.github.com>

Author: MattyTheHacker

.github/workflows/autoupdate.yaml

@@ -10,9 +10,16 @@ jobs:
       pull-requests: write
       contents: write
     steps:
-      - uses: CSSUoB/pr-auto-updater@v2.2.2
+      - name: Generate Access Token
+        uses: actions/create-github-app-token@v2
+        id: generate-token
+        with:
+          app-id: ${{ secrets.PR_AUTO_UPDATE_CLIENT_ID }}
+          private-key: ${{ secrets.PR_AUTO_UPDATE_PRIVATE_KEY }}
+
+      - uses: CSSUoB/pr-auto-updater@v2.1.2
         env:
-          GITHUB_TOKEN: '${{ secrets.PR_AUTO_UPDATE_TOKEN }}'
+          GITHUB_TOKEN: ${{ steps.generate-token.outputs.token }}
           PR_FILTER: 'labelled'
           PR_LABELS: 'sync'
           MERGE_CONFLICT_ACTION: 'label'