Hide close button on single file shares that have hide download enabled

[juliusknorr]

Only thing I noticed is that you close a read-only watermarked file, you get a pretty bare view.

Screenshot:

Might be something to look into with the design team after this PR is merged :)

Originally posted by @Raudius in #2579 (review)

[ananyak19]

Hey, I want to work on this.. can you give some more insight about what exactly needs to be done.