Fix uploading of emojis

[DEVTomatoCake]

I broke this in #1146

server/src/api/routes/guilds/#guild_id/emojis.ts

Line 128 in 143cbf2

const mimeType = body.image.split(":")[1].split(";")[0];

requires body.image to be the original one, not the hash. As the hash is never used (Emoji doesn't have any image property) it's pointless to update the value.