efi: Add iMac Pro 2017 to uefi skip cert quirk

The iMac Pro 2017 is also a T2 Mac. Thus add it to the list of uefi skip
cert.

Cc: stable@vger.kernel.org
Fixes: 155ca952

 ("efi: Do not import certificates from UEFI Secure Boot for T2 Macs")
Link: https://lore.kernel.org/linux-integrity/9D46D92F-1381-4F10-989C-1A12CD2FFDD8@live.com/
Signed-off-by: Aditya Garg <gargaditya08@live.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>