chore(deps): update dependency sinon to v7 (#219)

Author: renovate[bot]

packages/google-cloud-vision/package.json

@@ -88,7 +88,7 @@
     "nyc": "^13.0.0",
     "power-assert": "^1.6.0",
     "prettier": "^1.13.6",
-    "sinon": "^6.0.1",
+    "sinon": "^7.0.0",
     "uuid": "^3.3.0"
   }
 }

packages/google-cloud-vision/samples/package.json

@@ -26,7 +26,7 @@
     "@google-cloud/storage": "^2.0.0",
     "ava": "^0.25.0",
     "proxyquire": "^2.0.1",
-    "sinon": "^6.0.1",
+    "sinon": "^7.0.0",
     "uuid": "^3.2.1"
   },
   "optionalDependencies": {