docs: update beta samples to v1 and style

[nnegrey]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

[codecov]

Codecov Report

Merging #553 into master will increase coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #553      +/-   ##
==========================================
+ Coverage   92.24%   92.33%   +0.08%     
==========================================
  Files          15       15              
  Lines       12433    12433              
  Branches      484      484              
==========================================
+ Hits        11469    11480      +11     
+ Misses        959      948      -11     
  Partials        5        5

Impacted Files	Coverage Δ
src/v1p4beta1/image_annotator_client.ts	88.82% <0%> (+1.24%)	⬆️

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