ci: Use FLATHUBBOT_TOKEN

For forks of public repos, github removes the ability to comment on a PR

.github/workflows/close-master-prs.yaml

@@ -2,7 +2,7 @@ name: Close PRs to master
 
 on:
   pull_request:
-    types: [opened, reopened, synchronize]
+    types: [opened, reopened, synchronize, edited]
     branches:
       - master
   workflow_dispatch:
@@ -16,7 +16,7 @@ jobs:
     steps:
       - name: Check and close
         env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_TOKEN: ${{ secrets.FLATHUBBOT_TOKEN }}
           COMMENT: >
               This PR is automatically closed because application submission
               PRs must be made against the new-pr branch. If this is done