♻️(front) increase classroom poll refetch interval

We want to increase the refetch poll interval on the classroom
dashboard. We increase it from 5 seconds to 45 seconds in a first time.

src/frontend/packages/lib_classroom/src/components/DashboardClassroom/index.tsx

@@ -68,7 +68,7 @@ const DashboardClassroom = ({ classroomId }: DashboardClassroomProps) => {
   const user = useCurrentUser((state) => state.currentUser);
   const canUpdate = context.permissions.can_update;
 
-  const classroomRefetchInterval = useRef(5000);
+  const classroomRefetchInterval = useRef(45000);
   const [classroomUrl, setClassroomUrl] = useState('');
   const [askUsername, setAskUsername] = useState(false);
   const [classroomJoined, setClassroomJoined] = useState(false);