Bug 21239: CSS regressions caused by SCSS move

Bug 21239: CSS regressions caused by SCSS move

This patch corrects some mistakes in staff-global.scss made during the
conversion from CSS.

To test, apply the patch and regenerate your CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).
Clear your browser cache if necessary.

View various forms in the staff client which have hints and required
fields, including:

- Notices & slips -> Modify notice
- Administration -> Budgets -> Modify budget

Verify that date format hints are positioned correctly. Try to submit
the form with empty required fields and verify that the "This field is
required" message is positioned correctly.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>