Update dependency mocha to v9

Author: renovate-bot

package.json

@@ -67,7 +67,7 @@
         "estree-walker": "^3.0.0",
         "locate-character": "^2.0.5",
         "magic-string": "^0.25.7",
-        "mocha": "^8.0.0",
+        "mocha": "^9.0.0",
         "nyc": "^15.1.0",
         "prettier": "^2.0.5",
         "prettier-plugin-svelte": "^2.3.0",