Bug 15758: [QA Follow-up] Remove onlymine from Plugin/Branches.pm

Bug 15758: [QA Follow-up] Remove onlymine from Plugin/Branches.pm

Hard to miss that one:
Template process failed: plugin error - Bareword "C4::Branch::onlymine" not allowed while "strict subs" in use at Koha/Template/Plugin/Branches.pm line 59.
Compilation failed in require at /usr/lib/perl5/Template/Plugins.pm line 206.

Removed OnlyMine from Plugin/Branches. Replaced by a template var in
cleanborrowers; it was used only once.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>