ci: remove release workflow during release freeze (#354)

Remove the release workflow entirely per go/hardened-gha step 7.
The publish job was already commented out in the hardened runners PR,
but removing the file aligns with the approach taken by
databricks-sql-python (PR #764) and other partner ecosystem repos.

The workflow will be restored when the release pipeline is re-enabled
via the NPM Release SOP and #unblock-releases-public approval.

Co-authored-by: Isaac

Author: shivam2680