Use RTDB emulator v4.9.0 (#6197)

* Update database-emulator.ts

* 4.9.0

Author: fredzqm

scripts/emulator-testing/emulators/database-emulator.ts

@@ -26,11 +26,11 @@ export class DatabaseEmulator extends Emulator {
 
   constructor(port = 8088, namespace = 'test-emulator') {
     super(
-      'firebase-database-emulator-v4.4.1.jar',
+      'firebase-database-emulator-v4.9.0.jar',
       // Use locked version of emulator for test to be deterministic.
       // The latest version can be found from database emulator doc:
       // https://firebase.google.com/docs/database/security/test-rules-emulator
-      'https://storage.googleapis.com/firebase-preview-drop/emulator/firebase-database-emulator-v4.6.0.jar',
+      'https://storage.googleapis.com/firebase-preview-drop/emulator/firebase-database-emulator-v4.9.0.jar',
       port
     );
     this.namespace = namespace;