webui: Do not allow empty pagination size
Pagination size must be required, the current validators are triggered after
form is submitted, thus the only way for check if data is not empty is by making
the field required.
Fixes: https://pagure.io/freeipa/issue/9192
Signed-off-by: Armando Neto <abiagion@redhat.com>
Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>