Refactor heartbeat color logic in UptimeStatusIsland component for improved status representation

- Adjusted the color mapping for heartbeat statuses to enhance clarity: changed DOWN to red, PENDING to yellow, and maintained UP as green.
- Simplified the logic for better readability and maintainability.

src/components/UptimeStatusIsland.jsx

@@ -11,10 +11,9 @@ function getStatusColor(validCert) {
 }
 
 function getHeartbeatColor(status) {
-  if (status === 1) return 'bg-green-600'; // UP
-  if (status === 0) return 'bg-red-600';   // DOWN
-  if (status === 2) return 'bg-yellow-400'; // PENDING
-  if (status === 3) return 'bg-blue-500';   // MAINTENANCE
+  if (status === 1) return 'bg-green-600';   // UP
+  if (status === 0) return 'bg-yellow-400';  // PENDING
+  if (status === 2) return 'bg-red-600';     // DOWN
   return 'bg-gray-300';
 }