Stop creating blurhash for images

We should stop using BlurHash now that we have ThumbHash.

BlurHash takes like 10x as long to create, is buggier, and looks worse.

Looks like we only need to set withBlurhash: false on a couple of calls to Room.sendImage().

cvwright@laptop circles-ios % grep Circles -d recurse -e sendImage -i
Circles/Views/Photo Galleries/PhotoGalleryView.swift:                                 try await room.sendImage(image: img)
Circles/Views/Photo Galleries/PhotosUploadView.swift:                        try await room.sendImage(image: img)
Circles/Views/Timeline/RoomMessageComposer.swift:                    let eventId = try await self.room.sendImage(image: img, caption: caption, withBlurhash: false, withThumbhash: true, replacing: self.editing)