Updated ARCore package version to 2.1.0-preview.4.

Packages/manifest.json

     "com.unity.package-manager-ui": "2.0.7",
     "com.unity.purchasing": "2.0.6",
     "com.unity.textmeshpro": "1.3.0",
-    "com.unity.xr.arcore": "2.1.0-preview.1",
+    "com.unity.xr.arcore": "2.1.0-preview.4",
     "com.unity.xr.arfoundation": "1.5.0-preview.2",
     "com.unity.xr.arkit": "2.1.0-preview.1",
     "com.unity.xr.arkit-face-tracking": "1.0.0-preview.3",