remove duplicated notification handling code

src/utils/echo/listeners/adminNotificationsListener.js

@@ -1,16 +1,21 @@
-export const adminNotificationsListener = (echo, userData, setNotifications, setunreadNotification, updatePendingMembers) => {
+export const adminNotificationsListener = (echo, userData, setNotifications, setUnreadNotification, updatePendingMembers) => {
     if (userData.isAdmin) {
         const channelName = "users.admin";
-        echo.private(channelName)
-            .listen(".users.registration", (event) => {
+
+        const handleNotification = (content) => {
             const newNotification = {
                 id: Date.now(),
-                    content: `Nouvelle demande d'inscription : ${event.user.name} ${event.user.lastname}`,
+                content,
                 created_at: Date.now(),
                 pivot: { unread: 1 }
             };
             setNotifications(prev => [newNotification, ...prev]);
-                setunreadNotification(true);
+            setUnreadNotification(true);
+        };
+
+        echo.private(channelName)
+            .listen(".users.registration", (event) => {
+                handleNotification(`Nouvelle demande d'inscription : ${event.user.name} ${event.user.lastname}`);
                 updatePendingMembers();
             });
         return channelName;