go: Update module gocloud.dev to v0.30.0

See merge request https://gitlab.com/gitlab-org/gitaly/-/merge_requests/5974



Merged-by: Quang-Minh Nguyen <qmnguyen@gitlab.com>
Approved-by: Quang-Minh Nguyen <qmnguyen@gitlab.com>
Co-authored-by: GitLab Renovate Bot <gitlab-bot@gitlab.com>