Merge pull request #15 from unity/update-to-xcode-11-beta-5

Updating ARKit packages to be compatible with Xcode 11 beta 5.

Packages/manifest.json

     "com.unity.timeline": "1.0.0",
     "com.unity.xr.arcore": "2.2.0-preview.2",
     "com.unity.xr.arfoundation": "2.2.0-preview.3",
-    "com.unity.xr.arkit": "2.2.0-preview.3",
-    "com.unity.xr.arkit-face-tracking": "1.1.0-preview.3",
+    "com.unity.xr.arkit": "2.2.0-preview.4",
+    "com.unity.xr.arkit-face-tracking": "1.1.0-preview.4",
     "com.unity.xr.legacyinputhelpers": "2.0.2",
     "com.unity.modules.ai": "1.0.0",
     "com.unity.modules.animation": "1.0.0",