deps: bump Unity and URP versions

Author: jsm174

package.json

@@ -7,10 +7,10 @@
     "Unity",
     "URP"
   ],
-  "unity": "2021.2",
-  "unityRelease": "7f1",
+  "unity": "2021.3",
+  "unityRelease": "0f1",
   "dependencies": {
-    "com.unity.render-pipelines.universal": "12.1.2",
+    "com.unity.render-pipelines.universal": "12.1.6",
     "org.visualpinball.engine.unity": "0.0.1-preview.106"
   },
   "author": "freezy <[email protected]>",