chore(deps): update dependency nyc to v13 (#153)

Author: renovate[bot]

packages/google-cloud-speech/package.json

@@ -97,7 +97,7 @@
     "intelli-espower-loader": "^1.0.1",
     "jsdoc": "^3.5.5",
     "mocha": "^5.2.0",
-    "nyc": "^12.0.2",
+    "nyc": "^13.0.0",
     "power-assert": "^1.6.0",
     "prettier": "^1.13.5",
     "safe-buffer": "^5.1.2",