fix: Fix to delete cookie when AppSubURL is non-empty (#30375)

Cookies may exist on "/subpath" and "/subpath/" for some legacy reasons (eg: changed CookiePath behavior in code). The legacy cookie should be removed correctly.

---------

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

services/auth/source/oauth2/store.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 
 	"code.gitea.io/gitea/modules/log"
+	session_module "code.gitea.io/gitea/modules/session"
 
 	chiSession "gitea.com/go-chi/session"
 	"github.com/gorilla/sessions"
@@ -65,7 +66,7 @@ func (st *SessionsStore) Save(r *http.Request, w http.ResponseWriter, session *s
 	chiStore := chiSession.GetSession(r)
 
 	if session.IsNew {
-		_, _ = chiSession.RegenerateSession(w, r)
+		_, _ = session_module.RegenerateSession(w, r)
 		session.IsNew = false
 	}