refactor: clean up unused packages

[JustinBeckwith]

Fixes #<issue_number_goes_here> (it's a good idea to open an issue first for discussion)

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

[callmehiphop]

I'm sorry if I murdered your other PR :<

[codecov]

Codecov Report

Merging #517 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #517   +/-   ##
=======================================
  Coverage   94.97%   94.97%           
=======================================
  Files          16       16           
  Lines         996      996           
  Branches       87       87           
=======================================
  Hits          946      946           
  Misses         42       42           
  Partials        8        8

Impacted Files	Coverage Δ
src/message-stream.ts	100% <ø> (ø)	⬆️
src/topic.ts	91.66% <100%> (ø)	⬆️
src/publisher.ts	100% <100%> (ø)	⬆️
src/subscription.ts	100% <100%> (ø)	⬆️
src/iam.ts	100% <100%> (ø)	⬆️
src/pubsub.ts	100% <100%> (ø)	⬆️

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