chore(deps): update dependency gts to ^0.9.0 (#355)

Author: renovate[bot]

packages/packages/google-gax/package.json

@@ -38,7 +38,7 @@
     "@types/through2": "^2.0.33",
     "chai": "*",
     "codecov": "^3.1.0",
-    "gts": "^0.8.0",
+    "gts": "^0.9.0",
     "ink-docstrap": "^1.3.2",
     "intelli-espower-loader": "^1.0.1",
     "istanbul": "~0.4.5",