fix(deps): update dependency dot-prop to v9

Author: renovate-bot

package.json

@@ -52,7 +52,7 @@
     "@google-cloud/promisify": "^4.0.0",
     "arrify": "^2.0.0",
     "concat-stream": "^2.0.0",
-    "dot-prop": "^6.0.0",
+    "dot-prop": "^9.0.0",
     "escape-string-regexp": "^4.0.0",
     "extend": "^3.0.2",
     "google-gax": "^4.0.3",