Remove image upload when selecting a new image upload

[MV-GH]

Pre-Flight checklist

• [X] Did you check to see if this issue already exists?
• [X] This is a single feature request. (Do not put multiple feature requests in one issue)
• [X] This is not a question or discussion. (Use https://lemmy.ml/c/jerboa for that)

Describe The Feature Request Below

Call the removal function when selecting a new image, or when canceling the post

[MV-GH]

This was original meant for banner/ icons but Lemmy does this now in the backend. So no longer needed clientside. I do think this would be useful for posts.