Bug 35395: Update DefaultPatronSearchMethod system preference description

Bug 35395: Update DefaultPatronSearchMethod system preference description

This updates the system preference description of DefaultPatronSearchMethod
so that it's clear that the preference applies to all patron
searches, including patron module search and auto-completes.

To test:
* Search for DefaultPatronSearchMethod system preference in administration
* Verify the setting is reflected in the filters of the patron search
* Apply patch
* Verify that the description now is now improved.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 373a3c764c94348ae30299927982552f675f7752)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>