fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-INFLIGHT-6095116

package.json

@@ -41,7 +41,7 @@
     "ajv-formats": "~2.1.1",
     "better-ajv-errors": "~1.2.0",
     "browser-specs": "~3.34.0",
-    "c8": "~7.12.0",
+    "c8": "~9.0.0",
     "chalk": "~5.2.0",
     "chalk-template": "~0.4.0",
     "compare-versions": "~5.0.0",