Update default GIT_LFS_VERSION

What does this MR do?

Updates the default value of GIT_LFS_VERSION

Why was this MR needed?

We're now using 3.4.0.

What's the best way to test this MR?

To my knowledge this MR doesn't have any impact in practice, as we already specify 3.4.0 explicitly.

What are the relevant issue numbers?

none