Merge branch 'enable-block-fork-mirrors-by-default' into 'master'

Enable `block_external_fork_network_mirrors` by default

See merge request gitlab-org/gitlab!65156

config/feature_flags/development/block_external_fork_network_mirrors.yml

@@ -5,4 +5,4 @@ rollout_issue_url:
 milestone: '14.0'
 type: development
 group: group::source code
-default_enabled: false
+default_enabled: true