ci: Replace token generator Action with official

Ref. tibdex/github-app-token#99

Author: antoineco

.github/workflows/update-merge.yml

@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - name: Impersonate update bot
-        uses: tibdex/github-app-token@v2
+        uses: actions/create-github-app-token@v1
         id: generate-token
         with:
           app_id: ${{ secrets.APP_ID }}

.github/workflows/update.yml

@@ -85,7 +85,7 @@ jobs:
           fi
 
       - name: Impersonate update bot
-        uses: tibdex/github-app-token@v2
+        uses: actions/create-github-app-token@v1
         id: generate-token
         if: steps.update-files.outputs.has_changes
         with: