Small UX improvement for the upload page

@josma pointed out that we may have an UX problem in our upload page. There are a few people who have for some reason uploaded their data normally, but also decided to manually create an entry which seems to be completely unnecessary. Examples:

It might not be clear to people that the 'Create entry'-button is completely optional, and should only be used rarely and with a specific intention. For a 'typical' user that has the data already at hand the only required action would be to upload their existing files, not creating any manual entries. I would suspect that due to the button popping out visually (blue primary color) and the suggestive name ('Create entry') people unintentionally click it without understanding their action further.