fix: DMChannel.recipient and User.dm_channel being None after calling User.create_dm

[davidhozic]

Summary

In the current version (v2.5.0.rc5) the User.dm_channel is None even after calling User.create_dm.
It is due to a recipient not being assigned to DMChannel.recipient.

import discord
import secret

client = discord.Client()

@client.event
async def on_ready():
    zajcek_user = await client.get_or_fetch_user(145196308985020416)
    print(zajcek_user.dm_channel)
    await zajcek_user.create_dm()
    print(zajcek_user.dm_channel)

    await client.close()

client.run(secret.TOKEN)

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[Lulalaby]

the current version is rc5 btw

[davidhozic]

the current version is rc5 btw

Oh sorry yeah, I am on rc5 actually.. just miswrote :D.