chore(deps): update dependency typescript to ~3.6.0 (#581)

Author: renovate-bot

packages/packages/google-gax/package.json

@@ -82,7 +82,7 @@
     "tar": "^4.4.10",
     "through2": "^3.0.0",
     "ts-loader": "^6.0.3",
-    "typescript": "~3.5.0",
+    "typescript": "~3.6.0",
     "webpack": "^4.34.0",
     "webpack-cli": "^3.3.4"
   },