Bump css-tree from 2.3.1 to 3.1.0

Close #1378.

This also drops the CSS patch for css-values-5, no longer needed.

I still don't fully grasp why dependabot did not propose the bump but I suspect
that is due to the fact that we also have css-tree as a peer dependency for the
`@webref/css` package (which is also a dependency for testing purpose)

Author: tidoust

ed/csspatches/css-values-5.json.patch

@@ -33,7 +33,7 @@
     "@webref/elements": "file:packages/elements",
     "@webref/events": "file:packages/events",
     "@webref/idl": "file:packages/idl",
-    "css-tree": "2.3.1",
+    "css-tree": "3.1.0",
     "flags": "0.2.2",
     "mocha": "11.0.1",
     "reffy": "18.0.0",

package-lock.json

@@ -12,6 +12,6 @@
   "license": "MIT",
   "main": "index.js",
   "peerDependencies": {
-    "css-tree": "^2.3.1"
+    "css-tree": "^3.1.0"
   }
 }