fix(deps): google-gax v2.17.0 with mTLS (#529)

Author: bcoe

packages/google-cloud-texttospeech/package.json

@@ -43,7 +43,7 @@
     "precompile": "gts clean"
   },
   "dependencies": {
-    "google-gax": "^2.12.0"
+    "google-gax": "^2.17.0"
   },
   "devDependencies": {
     "@types/mocha": "^8.0.0",