Update MapLibre to version 4 (#872)

This updates maplibre from a pre-release to an official release.
It also removed the pre.2 from maputnik as maputnik is now published and
there's no reason to keep it in pre-release version name.
This doesn't mean maputnik has an npm package at this point though.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "maputnik",
-  "version": "2.0.0-pre.2",
+  "version": "2.0.0",
   "description": "A MapLibre GL visual style editor",
   "type": "module",
   "main": "''",
@@ -44,7 +44,7 @@
     "lodash.isequal": "^4.5.0",
     "lodash.throttle": "^4.1.1",
     "mapbox-gl-inspect": "^1.3.1",
-    "maplibre-gl": "^4.0.0-pre.4",
+    "maplibre-gl": "^4.0.0",
     "maputnik-design": "github:maputnik/design#172b06c",
     "ol": "^6.14.1",
     "ol-mapbox-style": "^7.1.1",