Revert "Use vector image for launcher icon."

app/src/main/AndroidManifest.xml

@@ -7,7 +7,7 @@
 
     <application
         android:allowBackup="true"
-        android:icon="@drawable/ic_launcher"
+        android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:theme="@style/AppTheme"
         android:networkSecurityConfig="@xml/network_security_config">