Regression: permission overwrite bits on old and new channel in channelUpdate are the same

[almostSouji]

Please describe the problem you are having in as much detail as possible:

Permission overwrites on old and new channel in channelUpdate are the same, making the permission bits from before the update inaccessible.

Include a reproducible code sample here, if possible:

client.on('channelUpdate', (o, n) => {
	if (o instanceof DMChannel || n instanceof DMChannel) return;
	console.log(inspect(o.permissionOverwrites.cache, { depth: 10 }));
	console.log(inspect(n.permissionOverwrites.cache, { depth: 10 }));
});

Steps to reproduce:

1. create channel
2. add permission overwrite for a user or role
3. observe same permission bits in the modified field allow/deny in both old and new channel

Further details:

regression introduced in #5318

• discord.js version: e7ad2fe
• Node.js version: v15.14.0
• Operating system: -
• Priority this issue should have – please be realistic and elaborate if possible: high
• I have also tested the issue on latest master, commit hash: 5b6be0c