update comment about skipping merged PRs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: skarim

cmd/checkout.go

@@ -471,8 +471,8 @@ func importRemoteStack(
 	}
 
 	// Create local branches for each PR's head branch.
-	// Skip merged PRs whose branches were deleted from the remote —
-	// these no longer exist upstream and can't be created locally.
+	// If creating a local branch for a merged PR fails, skip it. This commonly
+	// happens when the PR branch was deleted from the remote after merge.
 	for _, pr := range prs {
 		branch := pr.HeadRefName
 		if git.BranchExists(branch) {