fix vs studio version

Author: jinliu9508

OneSignalExample/Packages/manifest.json

@@ -5,7 +5,7 @@
     "com.onesignal.unity.ios": "file:../../com.onesignal.unity.ios",
     "com.unity.ai.navigation": "1.1.4",
     "com.unity.ide.rider": "3.0.24",
-    "com.unity.ide.visualstudio": "2.0.18",
+    "com.unity.ide.visualstudio": "2.0.16",
     "com.unity.ide.vscode": "1.2.5",
     "com.unity.test-framework": "1.1.33",
     "com.unity.textmeshpro": "3.0.6",