keep-workflows-enabled: Use GH_TOKEN_NEXTSTRAIN_BOT_WORKFLOW_DISPATCH

Used for `repo` scope token to work across different repositories.
Outside of this commit, I had to allow the `.github` repository to use
the organization secret.

.github/workflows/keep-workflows-enabled.yaml

@@ -15,7 +15,7 @@ jobs:
     permissions:
       actions: write
     env:
-      GH_TOKEN: ${{ github.token }}
+      GH_TOKEN: ${{ secrets.GH_TOKEN_NEXTSTRAIN_BOT_WORKFLOW_DISPATCH }}
     name: enable-workflow (${{ matrix.repo }}/${{ matrix.workflow }})
     strategy:
       fail-fast: false