Bug 27027: Fixed typo - extra dot removed

Bug 27027: Fixed typo - extra dot removed

Test Plan
Before applying patch
1. Open koha-tmpl/intranet-tmpl/prog/en/modules/admin/background_jobs.tt
2. Note how in line 125 "has successfully been modified.." has two full
stops
3. Apply patch
4. Repeat step 1
5. Note how there is only now one full stop in line 125 "has been
successfully ben modified."

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