chore(deps): update dependency sinon to v6.3.3 (#79)

* chore(deps): update dependency sinon to v6.3.3

* Update package.json

Author: renovate[bot]

cloud-tasks/package.json

@@ -16,14 +16,14 @@
   "dependencies": {
     "@google-cloud/tasks": "^0.2.2",
     "body-parser": "^1.18.3",
-    "express": "4.16.3",
+    "express": "^4.16.3",
     "yargs": "^12.0.1"
   },
   "devDependencies": {
-    "@google-cloud/nodejs-repo-tools": "2.3.0",
+    "@google-cloud/nodejs-repo-tools": "^2.3.0",
     "ava": "^0.25.0",
-    "proxyquire": "2.0.1",
-    "sinon": "6.0.1"
+    "proxyquire": "^2.0.1",
+    "sinon": "^6.3.3"
   },
   "cloud-repo-tools": {
     "requiresKeyFile": true,