chore(deps): update dependency google-cloud-texttospeech to v2.8.0 (#299)

Author: renovate-bot

translation/samples/snippets/hybrid_glossaries/requirements.txt

@@ -1,3 +1,3 @@
 google-cloud-translate==3.6.1
 google-cloud-vision==2.6.2
-google-cloud-texttospeech==2.7.1
+google-cloud-texttospeech==2.8.0