chore(deps): update dependency sinon to v5.1.1 (#151)

Author: renovate[bot]

error-reporting/package-lock.json

@@ -18,15 +18,15 @@
     "test": "npm run cover"
   },
   "dependencies": {
-    "@google-cloud/error-reporting": "0.5.0",
-    "express": "4.16.3",
-    "yargs": "11.0.0"
+    "@google-cloud/error-reporting": "^0.5.0",
+    "express": "^4.16.3",
+    "yargs": "^11.0.0"
   },
   "devDependencies": {
-    "@google-cloud/nodejs-repo-tools": "2.3.0",
-    "ava": "0.25.0",
-    "nyc": "11.8.0",
-    "proxyquire": "2.0.1",
-    "sinon": "5.0.7"
+    "@google-cloud/nodejs-repo-tools": "^2.3.0",
+    "ava": "^0.25.0",
+    "nyc": "^11.8.0",
+    "proxyquire": "^2.0.1",
+    "sinon": "^5.1.1"
   }
 }