fix(GuildMemberManager): add() method throws an error

[Syjalo]

Please describe the changes this PR makes and why it should be merged:
@discordjs/rest now returns an instance of Uint8Array

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

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1 Ignored Deployment

Name	Status	Preview	Updated
discord-js	⬜️ Ignored (Inspect)		Aug 21, 2022 at 7:03PM (UTC)

[codecov]

Codecov Report

Merging #8539 (a0cfd2f) into main (8028813) will increase coverage by 7.72%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #8539      +/-   ##
==========================================
+ Coverage   78.73%   86.45%   +7.72%     
==========================================
  Files          22       87      +65     
  Lines        3503     8462    +4959     
  Branches      320     1105     +785     
==========================================
+ Hits         2758     7316    +4558     
- Misses        741     1103     +362     
- Partials        4       43      +39     

Flag	Coverage Δ
builders	100.00% <ø> (?)
collection	100.00% <ø> (?)
proxy	73.28% <ø> (?)
rest	92.53% <ø> (ø)
utilities	100.00% <ø> (?)
voice	64.08% <ø> (?)
ws	59.57% <ø> (ø)

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

Impacted Files	Coverage Δ
.../src/interactions/slashCommands/options/integer.ts	100.00% <0.00%> (ø)
packages/builders/src/components/Component.ts	100.00% <0.00%> (ø)
.../interactions/slashCommands/SlashCommandBuilder.ts	100.00% <0.00%> (ø)
...ges/builders/src/components/textInput/TextInput.ts	100.00% <0.00%> (ø)
.../src/interactions/slashCommands/options/boolean.ts	100.00% <0.00%> (ø)
packages/voice/src/networking/Networking.ts	3.18% <0.00%> (ø)
packages/builders/src/util/normalizeArray.ts	100.00% <0.00%> (ø)
...ApplicationCommandNumericOptionMinMaxValueMixin.ts	100.00% <0.00%> (ø)
...s/src/interactions/slashCommands/options/string.ts	100.00% <0.00%> (ø)
...ashCommands/mixins/ApplicationCommandOptionBase.ts	100.00% <0.00%> (ø)
... and 55 more

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