Stop passing site cfg files via --param to llvm-lit.

This has been unnecessary since https://reviews.llvm.org/D37756.

https://reviews.llvm.org/D37838 removed it for llvm.

This removes it from clang, lld, clang-tools-extra (and the GN build).

No intended behavior change.

Differential Revision: https://reviews.llvm.org/D77585