Upgrade Mocha

Author: marijnh

package.json

@@ -23,7 +23,7 @@
   },
   "devDependencies": {
     "ist": "^1.0.0",
-    "mocha": "^3.0.2",
+    "mocha": "^9.1.2",
     "prosemirror-test-builder": "^1.0.0",
     "rollup": "^2.26.3",
     "@rollup/plugin-buble": "^0.21.3"