Bug 9765 - Remove unused include file: budgetperiods-admin.inc

budgetperiods-admin.inc doesn't appear to be used anywhere in Koha. This
patch removes it.

To test, confirm that a search for references to budgetperiods-admin.inc
returns no results.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>