Paste uploader does not catch when dms are closed

[onerandomusername]

We're not catching or responding when a user cannot be DMed when uploading a paste message: we should try/catch the author.send() method.

I don't know what behaviour we should have regarding deleting the paste, continuing with the upload, or what we should do if DMs are closed.

bot/bot/exts/utils/attachment_pastebin_uploader.py

Line 131 in 2640aaa

await message.author.send(content=f"[Click here](<{paste_response.removal}>) to delete your recent paste.")

related to #3422

[jb3]

The user has already reacted to say they want it uploaded, having the deletion link is a nicety but isn't required, DevOps can still delete pastes or they expire after a period, it's not the end of the world.