editMessage and editWebhookMessage send attachments twice in the same request

[TheEssem]

When using Client#editMessage, Client#editWebhookMessage, or anything that depends on these functions (e.g. CommandInteraction#editOriginalMessage), the file key is not stripped from the input object. This results in attachments being sent over simultaneously in raw binary form via the file form data entry, and as a JSON array converted from a Node buffer in the payload_data entry:

This can result in requests that are much larger than they should be (e.g. a 4MB request being inflated to 16MB). It would probably be a good idea to remove file from the options object in RequestHandler#request if the file argument is also present.

[bsian03]

#1285 resolves this