Bump @google-cloud/text-to-speech from 6.3.0 to 6.4.0

Bumps [@google-cloud/text-to-speech](https://github.com/googleapis/google-cloud-node/tree/HEAD/packages/google-cloud-texttospeech) from 6.3.0 to 6.4.0.
- [Release notes](https://github.com/googleapis/google-cloud-node/releases)
- [Changelog](https://github.com/googleapis/google-cloud-node/blob/main/packages/google-cloud-texttospeech/CHANGELOG.md)
- [Commits](https://github.com/googleapis/google-cloud-node/commits/dlp-v6.4.0/packages/google-cloud-texttospeech)

---
updated-dependencies:
- dependency-name: "@google-cloud/text-to-speech"
  dependency-version: 6.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -14,7 +14,7 @@
   },
   "dependencies": {
     "@google-cloud/speech": "^7.2.0",
-    "@google-cloud/text-to-speech": "^6.3.0",
+    "@google-cloud/text-to-speech": "^6.4.0",
     "@keyv/sqlite": "^4.0.5",
     "@langchain/anthropic": "^0.3.28",
     "@langchain/community": "^0.3.56",