TF-1217 Change fcm capability

fcm/lib/method/get/firebase_subscription_get_method.dart

@@ -22,7 +22,7 @@ class FirebaseSubscriptionGetMethod extends GetMethodNoNeedAccountId {
   @override
   Set<CapabilityIdentifier> get requiredCapabilities => {
     CapabilityIdentifier.jmapCore,
-    FirebaseCapability.identifier,
+    FirebaseCapability.fcmIdentifier,
   };
 
   @override

fcm/lib/method/set/firebase_subscription_set_method.dart

@@ -16,7 +16,7 @@ class FirebaseSubscriptionSetMethod extends SetMethodNoNeedAccountId<FirebaseSub
   @override
   Set<CapabilityIdentifier> get requiredCapabilities => {
     CapabilityIdentifier.jmapCore,
-    FirebaseCapability.identifier
+    FirebaseCapability.fcmIdentifier
   };
 
   @override

fcm/lib/model/firebase_capability.dart

@@ -1,8 +1,6 @@
 
 import 'package:jmap_dart_client/jmap/core/capability/capability_identifier.dart';
 
-class FirebaseCapability extends CapabilityIdentifier {
-  static final identifier = FirebaseCapability(Uri.parse('com:linagora:params:jmap:firebase:push'));
-
-  FirebaseCapability(super.value);
+class FirebaseCapability {
+  static final fcmIdentifier = CapabilityIdentifier(Uri.parse('com:linagora:params:jmap:firebase:push'));
 }