Is your feature request related to a problem? Please describe.
Since it's not currently possible to change image attachments, if the first message contains an image attachement, then the lack of a delete button on the first message means it's not even possible to change the image of the first message by deleting it and starting again.

Describe the solution you'd like
Allow deleting the first message.

Describe alternatives you've considered
Delete the chat and start a new one.

Additional context
This wouldn't really be needed if it were possible to edit image attachments, but I'd still prefer the simplicity & UX consistency of being able to delete any message I want.