refactor(GuildChannel): simplify constructor

[kyranet]

Please describe the changes this PR makes and why it should be merged:

• this.parentId = this.parentId ?? null was an useless call since this.parentId is undefined at construct (as the parent class doesn't assign it either), therefore the check was moved to the _patch method with a default, consistent with the rest of structures.
• guild?.client is an unnecessary check when client is already passed and always guaranteed to exist. Removing this check allows us to reduce some overhead when creating channels.

🤖 Generated by Copilot at 6a83a0f

Oh we're the coders of the sea, and we like to keep things neat
We simplify the GuildChannel class, and make the parentId complete
We use the nullish operators, to avoid the extra work
And when we're done we push the code, and give ourselves a smirk

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

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

2 Ignored Deployments

Name	Status	Preview	Comments	Updated (UTC)
discord-js	⬜️ Ignored (Inspect)			May 2, 2023 9:38am
discord-js-guide	⬜️ Ignored (Inspect)			May 2, 2023 9:38am