Fix update by rebase being wrongly disabled by protected base branch (#…

…22825)

The branch this is force pushing to is the head branch in the head repo,
so it should be checking if that is protected, not the base.

services/pull/update.go

@@ -106,7 +106,7 @@ func IsUserAllowedToUpdate(ctx context.Context, pull *issues_model.PullRequest,
  BaseBranch: pull.HeadBranch,
  }
 
- pb, err := git_model.GetFirstMatchProtectedBranchRule(ctx, pull.BaseRepoID, pull.BaseBranch)
+ pb, err := git_model.GetFirstMatchProtectedBranchRule(ctx, pr.BaseRepoID, pr.BaseBranch)
  if err != nil {
  return false, false, err
  }