android notif: Replace hardcoded applicationId with variable

As stated in google docs and Stackoverflow the category name of the
GCM reciever intent-filter should match with the package name
Link: https://stackoverflow.com/a/13445847/5026681

android/app/src/main/AndroidManifest.xml

@@ -66,7 +66,7 @@
             tools:selector="com.wix.reactnativenotifications">
             <intent-filter>
                 <action android:name="com.google.android.c2dm.intent.RECEIVE" />
-                <category android:name="com.zulipmobile" />
+                <category android:name="${applicationId}" />
                 <action android:name="com.google.android.c2dm.intent.REGISTRATION" />
             </intent-filter>
         </receiver>