chore: release 4.6.0 (#788)

🤖 I have created a release \*beep\* \*boop\*
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## [4.6.0](https://www.github.com/googleapis/nodejs-speech/compare/v4.5.6...v4.6.0) (2021-08-10)


### Features

* add total_billed_time response field ([#787](https://www.github.com/googleapis/nodejs-speech/issues/787)) ([171cba0](https://www.github.com/googleapis/nodejs-speech/commit/171cba0bb8f7bd12ab96f296824e0acf7a0698d7))
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This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).

speech/package.json

@@ -15,7 +15,7 @@
     "test": "c8 mocha system-test --timeout 600000"
   },
   "dependencies": {
-    "@google-cloud/speech": "^4.5.6",
+    "@google-cloud/speech": "^4.6.0",
     "@google-cloud/storage": "^5.0.0",
     "chalk": "^4.0.0",
     "node-record-lpcm16": "^1.0.1",