docs: fix Self-Hosted GitLab installation requirements

Add GitLab Runner installation requirement for Self-Hosted GitLab section

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: d-bytebase

mintlify/gitops/installation.mdx

@@ -46,8 +46,8 @@ When using cloud VCS with self-hosted Bytebase, you need a self-hosted runner:
 
 ### Self-Hosted GitLab
 
-No runner installation needed. Simply ensure:
-- VPC connectivity between GitLab and Bytebase servers
+- Install a [GitLab Runner](https://docs.gitlab.com/runner/) on your GitLab server
+- Ensure VPC connectivity between GitLab and Bytebase servers
 - Network policies allow communication
 - If your GitLab runner lacks internet access, pre-load the bytebase-action Docker image