If the "Frequently visited" list needs more space than the given, its content is now scrollable. 
This only affects the "Frequently visited" not the search results.

This reverts merge request !14768

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/38315
Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/38187

- Cleans the fork project layout by removing the grid & reverting back
to full flexbox to allow for the layout to correctly expand.
- Removes duplicated markup
- Fixes a bug where the forked project would trigger the load indicator

Closes #38411