[CDF-26325] ⚠Remove filemetadata upload (#2265)

# Description

Removing upload option from FileMetadata. This is because if you upload
a classic file without content in CDF, it will be deleted. Thus, there
is no point to do it.

## Bump

- [x] Patch
- [ ] Skip

## Changelog

### Improved

- You can no longer upload files without content. This is because files
without content get automatically deleted in CDF, and thus should not be
uploaded.
