message: fix(/chat): retire invitation link and use public server link
diff: /blog/gitlab-integration/+ /blog/gitlab-integration 301
  /careers https://gitpod.crew.work/jobs 301
  -/chat https://discord.gg/ZZ8wxgHtc6 301
  +/chat https://discord.com/invite/gitpod 301
  /cla https://www.github.com/gitpod-io/cla
  /code-of-conduct https://github.com/gitpod-io/.github/blob/main/CODE_OF_CONDUCT.md
  /configure/editor /docs/editors/vscode 301
  