chore(deps): update dependency google-cloud-texttospeech to v2.5.0 (#160)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [google-cloud-texttospeech](https://togithub.com/googleapis/python-texttospeech) | `==2.4.0` -> `==2.5.0` | [![age](https://badges.renovateapi.com/packages/pypi/google-cloud-texttospeech/2.5.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/google-cloud-texttospeech/2.5.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/google-cloud-texttospeech/2.5.0/compatibility-slim/2.4.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/google-cloud-texttospeech/2.5.0/confidence-slim/2.4.0)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>googleapis/python-texttospeech</summary>

### [`v2.5.0`](https://togithub.com/googleapis/python-texttospeech/blob/master/CHANGELOG.md#&#8203;250-httpswwwgithubcomgoogleapispython-texttospeechcomparev240v250-2021-07-01)

[Compare Source](https://togithub.com/googleapis/python-texttospeech/compare/v2.4.0...v2.5.0)

##### Features

-   add always_use_jwt_access ([#&#8203;155](https://www.github.com/googleapis/python-texttospeech/issues/155)) ([cd10c37](https://www.github.com/googleapis/python-texttospeech/commit/cd10c3704db610f2abf65c9142cfdaa867d8490a))

##### Bug Fixes

-   disable always_use_jwt_access ([#&#8203;159](https://www.github.com/googleapis/python-texttospeech/issues/159)) ([d109303](https://www.github.com/googleapis/python-texttospeech/commit/d109303898facc663a6e7fe9212440831c1eeb75))

##### Documentation

-   omit mention of Python 2.7 in 'CONTRIBUTING.rst' ([#&#8203;1127](https://www.github.com/googleapis/python-texttospeech/issues/1127)) ([#&#8203;150](https://www.github.com/googleapis/python-texttospeech/issues/150)) ([d2954ba](https://www.github.com/googleapis/python-texttospeech/commit/d2954ba91385db6d581f75154fb11c969f6ca0e2)), closes [#&#8203;1126](https://www.github.com/googleapis/python-texttospeech/issues/1126)

</details>

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Author: renovate-bot

texttospeech/snippets/requirements.txt

@@ -1,2 +1,2 @@
 future==0.18.2
-google-cloud-texttospeech==2.4.0
+google-cloud-texttospeech==2.5.0