Use direct link instead of JS

Due to our CSP policy this link won’t work as it it considered as
inline Javascript.

This commit replaces the link with a static link to the files app.

Reimplementation of #8067 - fixes #7742
Link to previous directory
Merge pull request #8203 from owncloud/correct-link

Use direct link instead of JS

* owncloud/correct-link:
  Link to previous directory
  Use direct link instead of JS