MDL-21933 course: Allow users to search participants course permission

Users who have the moodle/course:viewpartiicpants should be able to
view the search items as they are already able to view the list.

Search is an expected feature for users and it was confusion to only
appear after 3 pages.  This has been changed to enable search when
there are more records than are visible on the screen.  If users
are unable to use browser search, they will be able to use Moodle's
search.