chore(texttospeech): modernize quickstart for texttospeech

[iennae]

Description

Fixes #3504

(draft, still requires test update, region tags not added yet intentionally)

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Checklist

• [x] I have followed guidelines from CONTRIBUTING.MD and Samples Style Guide
• [x] Tests pass: npm test (see Testing)
• [x] Lint pass: npm run lint (see Style)
• [x] This pull request is from a branch created directly off of GoogleCloudPlatform/nodejs-docs-samples. Not a fork.
• [ ] Please merge this PR for me once it is approved