Merge pull request #50 from unity/fix-preview2-issues

Updating ARFoundation packages to 4.0.0-preview.3.

Packages/manifest.json

     "com.unity.test-framework": "1.1.14",
     "com.unity.textmeshpro": "2.0.1",
     "com.unity.ugui": "1.0.0",
-    "com.unity.xr.arcore": "4.0.0-preview.2",
-    "com.unity.xr.arfoundation": "4.0.0-preview.2",
-    "com.unity.xr.arkit": "4.0.0-preview.2",
-    "com.unity.xr.arkit-face-tracking": "4.0.0-preview.2",
+    "com.unity.xr.arcore": "4.0.0-preview.3",
+    "com.unity.xr.arfoundation": "4.0.0-preview.3",
+    "com.unity.xr.arkit": "4.0.0-preview.3",
+    "com.unity.xr.arkit-face-tracking": "4.0.0-preview.3",
     "com.unity.modules.ai": "1.0.0",
     "com.unity.modules.androidjni": "1.0.0",
     "com.unity.modules.animation": "1.0.0",