refactor: replace once with onetime

[callmehiphop]

We saw some issues with the latest version of @types/node. Turns out there was a conflict with EventEmitter#once and the types for the once module. This PR just swaps once out for a similar module that does not extend Function.prototype.

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

[codecov]

Codecov Report

Merging #660 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #660   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files           9        9           
  Lines         869      869           
  Branches       99       99           
=======================================
  Hits          851      851           
  Misses          9        9           
  Partials        9        9

Impacted Files	Coverage Δ
src/file.ts	98.64% <100%> (ø)	⬆️

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[codecov]

Codecov Report

Merging #660 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #660   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files           9        9           
  Lines         869      869           
  Branches       99       99           
=======================================
  Hits          851      851           
  Misses          9        9           
  Partials        9        9

Impacted Files	Coverage Δ
src/file.ts	98.64% <100%> (ø)	⬆️

---

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 3041d15...37f8529. Read the comment docs.