ci: make module releases compatible with immutable releases

[intel352]

Summary

• remove post-publish release asset upload/delete from module-release workflow
• keep module release/tag creation and Go proxy announcement flow intact
• avoid GitHub immutable-release 422 failures caused by mutating release assets after publish

Verification

• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/module-release.yml"); puts "yaml ok"'
• git diff --check
• actionlint scoped check for edited release block produced no findings

Full actionlint still reports pre-existing shellcheck warnings elsewhere in module-release.yml.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Copilot]

Pull request overview

Updates the module release GitHub Actions workflow to be compatible with GitHub “immutable releases” by removing post-publish release asset mutations while preserving the existing release/tag creation and Go proxy announcement behavior.

Changes:

• Remove post-publish gh release upload and gh release delete-asset steps to avoid immutable-release 422 failures.
• Keep release creation, git tag creation/push, and Go proxy announcement flow intact.
• Minor hardening/readability improvements by assigning key values to variables and consistently quoting them.