Fix incorrect redirection when creating a PR fails (#29537) (#29543)

Backport #29537 by wxiaoguang

This is only a quick fix to make it easier to backport.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/diff/compare.tmpl

@@ -11,14 +11,6 @@
 			{{ctx.Locale.Tr "action.compare_commits_general"}}
 		{{end}}
 	</h2>
-	{{if .Flash.WarningMsg}}
-		{{/*
-			There's already an importing of alert.tmpl in new_form.tmpl,
-			but only the negative message will be displayed within forms for some reasons, see semantic.css:10659.
-			To avoid repeated negative messages, the importing here if for .Flash.WarningMsg only.
-		*/}}
-		{{template "base/alert" .}}
-	{{end}}
 	{{$BaseCompareName := $.BaseName -}}
 	{{- $HeadCompareName := $.HeadRepo.OwnerName -}}
 	{{- if and (eq $.BaseName $.HeadRepo.OwnerName) (ne $.Repository.Name $.HeadRepo.Name) -}}