Bug 29195: Fix highlighting on odd rows in circ-patron-search-results

Bug 29195: Fix highlighting on odd rows in circ-patron-search-results

This patch adds "!important" to the CSS rule governing the background
color of table cells when hovered. It only applies to tables with the
"selections-table" class.

Although "!important" is not usually recommended, in this case the
appliation is narrow enough that I think it outweighs the complicated
selector that would be required to make it work otherwise.

To test, apply the patch and rebuild the staff interface CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

- Locate a record in the catalog and being the process of placing a
  hold.
- When you're asked to enter a card number or search by name, search
  using a name which will return multiple results.
- In the table of results, hovering the mouse over the table should
  highlight the row in yellow.
- Perform the same test when searching for a club by name.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>