ci: remove stale publish.yaml workflow

publish.yaml started failing on every push to main with a startup error:
the workflow it calls (PowerShellOrg/.github powershell-release.yml@main)
no longer accepts the isPrerelease input — #468 replaced it with force —
and publish.yaml also omits the now-required module-name.

publish.yaml is a leftover duplicate of release.yml, which is the
canonical tag-triggered release workflow. The push-to-main auto-publish
model it implemented was superseded by the tag/dispatch flow in #468.
Remove it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: HeyItsGilbert