fix: grant workflows: write permission to update-template CI job

[Copilot]

The Update Template CI job fails when pushing regenerated workflow files because GITHUB_TOKEN lacks the workflows permission by default, and the job falls back to it when GH_PAT is absent or insufficient.

Changes

• .github/workflows/update-template.yml: Added explicit permissions block to the job:

permissions:
  contents: write
  workflows: write

Without workflows: write, GitHub rejects any push that creates or modifies files under .github/workflows/, which is exactly what upptime/uptime-monitor update-template does on every run.