Remove vue2-dropzone package

[LukasHirt]

Description

Remove vue2-dropzone package from files app since we don't really use it's features and what we use from it can be replaced with events.

[pascalwengerter]

@LukasHirt did you re-introduce vue2-dropzone in the evil PR (or decided to keep it, after all)?

[LukasHirt]

It was never removed, was it?

[pascalwengerter]

Nope. My understanding was that at some point in history it might've been possible (after #2239 was merged) but it seems to be a valid part of the application (again)? Then we can possibly close the issue

[LukasHirt]

When implementing the dropzone originally we used the mentioned lib. We are using only a super limited set of features that are easily replaced with native events so we do not need that lib. This ticket is not about removing the dropzone itself. Only the lib under the hood should be removed and replaced with those native events...

[pascalwengerter]

I see, thanks for clarification!

[pascalwengerter]

Closing in favor of #6019