Remove recurring Discord invite check workflow

[Copilot]

The repository was emitting repeated CI failures/notifications from the Check Discord invite link workflow triggered on schedule and manual dispatch. This PR removes that workflow so those recurring failures stop.

• Workflow cleanup

  • Removed .github/workflows/check-discord-link.yml from the repository.
  • Eliminates both periodic and on-demand execution paths for Discord invite validation.

• Operational impact

  • Stops the recurring Check Discord invite link failure runs.
  • Prevents further noise from that workflow’s error/issue-creation path.

# Removed workflow triggers
on:
  schedule:
    - cron: '0 */12 * * *'
  workflow_dispatch: