Update manifest.json

Packages/manifest.json

     "com.unity.timeline": "1.1.0",
     "com.unity.ugui": "1.0.0",
     "com.unity.xr.arcore": "3.1.0-preview.2",
-    "com.unity.xr.arfoundation": "3.1.0-preview.2",
+    "com.unity.xr.arfoundation": "3.1.0-preview.3",
     "com.unity.xr.arkit": "3.1.0-preview.2",
     "com.unity.xr.arkit-face-tracking": "3.1.0-preview.2",
     "com.unity.xr.legacyinputhelpers": "2.0.6",