Remove UEFI condition from shim-x64 workaround

jcarneir-redhat.com bumped into the issue when he had the shim-x64 package installed on a BIOS-based system.

As of now, Convert2RHEL only handles this case on UEFI-based systems, as we haven't seen any case of shim-x64 packages on a BIOS-based system. This way, we need to improve the code that handles the workaround for the shim-x64 package and make sure that the same behavior is working for a BIOS system.

Acceptance Criteria

• Remove the condition from the shim-x64 workaround that skips it on non-UEFI based systems.
• It's covered by an integration test.