Unpin uguid dependency

[phip1611]

We should unpin the dependency and bump the MSRV of uefi-raw.

Context: #1650

[phip1611]

Technically still pinned with the = modifier https://github.com/rust-osdev/uefi-rs/pull/1653/files

[nicholasbishop]

Ah, right you are. Put up #1673