fix(deps): update dependency dot-prop to v5 (#455)

Author: renovate[bot]

package.json

@@ -54,7 +54,7 @@
     "@google-cloud/promisify": "^0.4.0",
     "arrify": "^2.0.0",
     "concat-stream": "^2.0.0",
-    "dot-prop": "^4.2.0",
+    "dot-prop": "^5.0.0",
     "escape-string-regexp": "^1.0.5",
     "extend": "^3.0.0",
     "google-auth-library": "^3.0.0",