[clang] [OpenMP] Change default version to OMP6.0. (PR #122108)

[Alexey Bataev via cfe-commits]

alexey-bataev wrote:

> > Not sure this level of support is enough to make 6.0 the default version. We're missing support for some 5.2 features still
> 
> That's what I thought! So the macro should continue being set to `202011?

I think yes, unless we support most of the 6.0 features

https://github.com/llvm/llvm-project/pull/122108