Fix rendered wiki page link (#31398) (#31407)

Backport #31398

Fix #31395

routers/web/repo/wiki.go

@@ -532,7 +532,7 @@ func Wiki(ctx *context.Context) {
 	}
 
 	wikiPath := entry.Name()
-	if markup.Type(wikiPath) != markdown.MarkupName {
+	if markup.DetectMarkupTypeByFileName(wikiPath) != markdown.MarkupName {
 		ext := strings.ToUpper(filepath.Ext(wikiPath))
 		ctx.Data["FormatWarning"] = fmt.Sprintf("%s rendering is not supported at the moment. Rendered as Markdown.", ext)
 	}