docs(samples): updated samples code to use async await

[praveenqlogic]

Fixes googleapis/google-cloud-node#2869 (it's a good idea to open an issue first for discussion)
Fixes https://github.com/googleapis/nodejs-language

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[JustinBeckwith]

@praveenqlogic it looks like many of the sample tests are failing. Let me know when I should take another look!

[codecov]

Codecov Report

Merging #154 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #154   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      1           
  Lines           5      5           
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  Hits            5      5

---

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[codecov]

Codecov Report

Merging #154 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #154   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      1           
  Lines           5      5           
=====================================
  Hits            5      5

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 66325b4...6172a93. Read the comment docs.