fix(deps): update dependency @google-cloud/text-to-speech to v4

Author: renovate-bot

samples/package.json

@@ -15,7 +15,7 @@
   },
   "dependencies": {
     "@google-cloud/automl": "^2.0.0",
-    "@google-cloud/text-to-speech": "^3.0.0",
+    "@google-cloud/text-to-speech": "^4.0.0",
     "@google-cloud/translate": "^7.0.0",
     "@google-cloud/vision": "^2.0.0",
     "yargs": "^16.0.0"