efi_loader: remove EFI_UNICODE_COLLATION_PROTOCOL

In EFI 1.10 a version of the Unicode collation protocol using ISO 639-2
language codes existed. This protocol is not part of the UEFI specification
any longer. It was however required to run the UEFI Self Certification Test
(SCT) II, version 2.6, 2017. So we implemented it for the sole purpose of
running the SCT.

As the SCT does not need the protocol anymore it is time for removal.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>