fix(release): make notes optional for create/update operations

Closes #8193 (closed)

Summary

Remove the validation that incorrectly required --notes or --notes-file in non-interactive mode. According to the GitLab API documentation and the client-go library, the description field is optional for both create and update operations.

What does this MR do?

This fix allows users to:

• Create releases without notes in non-interactive mode
• Update existing releases (e.g., to change --released-at) without providing notes, since the release already has notes

Changes

• Remove the noteProvided validation in complete()
• Remove unused errors import
• Add tests for both create and update without notes

Related issues

Fixes #8193 (closed)