Update dependency c8 to v8 (#443)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package-lock.json

@@ -34,7 +34,7 @@
     "@types/mocha": "^7.0.2",
     "@types/node": "^14.18.26",
     "ava": "^5.0.0",
-    "c8": "^7.10.0",
+    "c8": "^8.0.0",
     "code-style": "github:OpenZeppelin/code-style",
     "hardhat": "^2.8.0",
     "openzeppelin-docs-utils": "github:OpenZeppelin/docs-utils",