build: use c8 for coverage (#381)

Author: JustinBeckwith

packages/google-cloud-compute/package.json

@@ -29,7 +29,7 @@
     "lint": "eslint '**/*.js'",
     "samples-test": "cd samples/ && npm link ../ && npm test && cd ../",
     "system-test": "mocha system-test/*.js --timeout 1200000",
-    "test": "nyc mocha",
+    "test": "c8 mocha",
     "fix": "eslint --fix '**/*.js'",
     "docs-test": "linkinator docs",
     "predocs-test": "npm run docs"
@@ -59,7 +59,7 @@
     "jsdoc-region-tag": "^1.0.2",
     "linkinator": "^1.5.0",
     "mocha": "^6.0.0",
-    "nyc": "^14.0.0",
+    "c8": "^7.0.0",
     "power-assert": "^1.5.0",
     "prettier": "^1.13.5",
     "proxyquire": "^2.0.1",