refactor: compare with undefined directly

[almeidx]

Please describe the changes this PR makes and why it should be merged:
Updated all of the typeof x === "undefined" into x === undefined (also !==) as it is needlessly verbose since in strict mode the only reason to use typeof is if x might not be declared

This also brings in more consistency since x === undefined was already being used in some places (!== too), e.g.

discord.js/packages/builders/src/interactions/slashCommands/mixins/ApplicationCommandOptionWithChoicesAndAutocompleteMixin.ts

Line 34 in dc142c4

if (this.choices === undefined) {

discord.js/packages/discord.js/src/managers/ChannelManager.js

Line 22 in dc142c4

this._cache.maxSize === undefined ||

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes

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[codecov]

Codecov Report

Merging #9191 (6cb9de7) into main (955e8fe) will not change coverage.
The diff coverage is 86.95%.

@@           Coverage Diff           @@
##             main    #9191   +/-   ##
=======================================
  Coverage   83.70%   83.70%           
=======================================
  Files         100      100           
  Lines        9550     9550           
  Branches     1101     1101           
=======================================
  Hits         7994     7994           
  Misses       1517     1517           
  Partials       39       39           

Flag	Coverage Δ
builders	98.25% <ø> (ø)
collection	100.00% <100.00%> (ø)
next	∅ <ø> (∅)
proxy	79.56% <ø> (ø)
rest	92.07% <ø> (ø)
voice	63.47% <50.00%> (ø)
ws	58.12% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/voice/src/networking/Networking.ts	3.18% <0.00%> (ø)
packages/voice/src/networking/VoiceWebSocket.ts	0.00% <0.00%> (ø)
packages/voice/src/receive/AudioReceiveStream.ts	100.00% <ø> (ø)
packages/voice/src/VoiceConnection.ts	81.76% <50.00%> (ø)
packages/collection/src/collection.ts	100.00% <100.00%> (ø)
packages/voice/src/DataStore.ts	98.14% <100.00%> (ø)
packages/voice/src/audio/AudioResource.ts	95.23% <100.00%> (ø)

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