fix(deps): require google-gax v2.12.0 (#740)

Author: alexander-fenster

packages/google-cloud-node/package.json

@@ -50,7 +50,7 @@
   "dependencies": {
     "@google-cloud/common": "^3.0.0",
     "@types/pumpify": "^1.4.1",
-    "google-gax": "^2.9.2",
+    "google-gax": "^2.12.0",
     "protobufjs": "^6.8.6",
     "pumpify": "^2.0.0",
     "stream-events": "^1.0.4",

packages/google-cloud-node/samples/README.md

@@ -199,14 +199,16 @@ __Usage:__
 
 ### Transcribe Context Classes
 
+Provides "hints" to the speech recognizer to favor specific words and phrases in the results.
+
 View the [source code](https://github.com/googleapis/nodejs-speech/blob/master/samples/transcribeContextClasses.js).
 
 [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/nodejs-speech&page=editor&open_in_editor=samples/transcribeContextClasses.js,samples/README.md)
 
 __Usage:__
 
 
-`node samples/transcribeContextClasses.js`
+`node samples/transcribeContextClasses.js <storageUri>`