Disable two_step_rebase feature flag

Disabling because of https://gitlab.com/gitlab-org/gitlab-ce/issues/62353

app/models/repository.rb

@@ -1077,7 +1077,7 @@ class Repository
   end
 
   def rebase(user, merge_request)
-    if Feature.disabled?(:two_step_rebase, default_enabled: true)
+    if Feature.disabled?(:two_step_rebase, default_enabled: false)
       return rebase_deprecated(user, merge_request)
     end
 

changelogs/unreleased/dm-disable-two-step-rebase.yml

+---
+title: Disable two-step rebase which could cause rebases to hang
+merge_request: 28778
+author:
+type: other