Improve user search display name (#29002)

I tripped over this strange method and I don't think we need that
workaround to fix the value.

old:

![grafik](https://github.com/go-gitea/gitea/assets/1666336/c8b6797b-eb45-4dec-99db-1b0649a34ec5)

new:

![grafik](https://github.com/go-gitea/gitea/assets/1666336/ab1a65ae-de5b-4ce4-9813-3b8b39c7922e)

---------

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

routers/utils/utils.go

@@ -11,14 +11,6 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 )
 
-// RemoveUsernameParameterSuffix returns the username parameter without the (fullname) suffix - leaving just the username
-func RemoveUsernameParameterSuffix(name string) string {
-	if index := strings.Index(name, " ("); index >= 0 {
-		name = name[:index]
-	}
-	return name
-}
-
 // SanitizeFlashErrorString will sanitize a flash error string
 func SanitizeFlashErrorString(x string) string {
 	return strings.ReplaceAll(html.EscapeString(x), "\n", "<br>")