Bug 12112: remove disused routine C4::Breeding::ImportBreeding()

Bug 12112: remove disused routine C4::Breeding::ImportBreeding()

This patch removes the ImportBreeding() routine, which lost its
last caller as of the patch for bug 10462.

To test:

[1] Verify that prove -v t/Breeding.t passes.
[2] Perform a Z39.50 search in the staff interface.
[3] Perform a cataloguing reservoir search in the staff
    interface; verifying that cached records from the search
    done in step 2 are retrieved.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 990bb17e14efb8a2c16236c89ef5869dcfc48ad4)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>