revert: remove publish-mcp.yml — consolidate to monorepo orchestrator

The mcp-server publish logic belongs in mixpeek/mixpeek's orchestrator
workflow, not scattered across SDK repos. Note: this workflow did
successfully publish mixpeek-mcp==0.1.1 to PyPI, but the same logic
will live in the monorepo going forward.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: esteininger