refactor(ci): only run release workflows on released event

[jsjoeio]

This PR updates the trigger event for both the "Publish on npm and brew" and the "Publish on Docker" release workflows so that they only run on released (instead of published).

Why is this change necessary?

In order for us to publish pre-releases without triggering these workflows, this change needs to happen.

We learned this through the GitHub Actions docs:

Note: The prereleased type will not trigger for pre-releases published from draft releases, but the published type will trigger. If you want a workflow to run when stable and pre-releases publish, subscribe to published instead of released and prereleased.

Fixes N/A
Related #4264

[github-actions]

✨ Coder.com for PR #4288 deployed! It will be updated on every commit.

• Host: https://codercom-10hizcgrj-codercom.vercel.app/docs/code-server
• Last deploy status: success
• Commit: 872bb81
• Workflow status: https://github.com/cdr/code-server/actions/runs/1400959060

[jsjoeio]

waiting on #4290

[jawnsy]

very interesting

[jsjoeio]

The build is failing and I'm not sure why. See logs. I'm going to investigate.

[codecov]

Codecov Report

Merging #4288 (872bb81) into main (946e4e8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #4288   +/-   ##
=======================================
  Coverage   66.29%   66.29%           
=======================================
  Files          31       31           
  Lines        1620     1620           
  Branches      316      316           
=======================================
  Hits         1074     1074           
  Misses        468      468           
  Partials       78       78           

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