fix(deps): use the latest extend (#678)

Author: JustinBeckwith

package.json

@@ -61,7 +61,7 @@
     "arrify": "^2.0.0",
     "checkpoint-stream": "^0.1.1",
     "events-intercept": "^2.0.0",
-    "extend": "^3.0.1",
+    "extend": "^3.0.2",
     "google-auth-library": "^5.0.0",
     "google-gax": "^1.0.0",
     "grpc": "^1.21.1",