[clang] [Driver] Remove a bunch of unnecessary REQUIRES constraints (PR #94055)

[Alexander Richardson via cfe-commits]

================
@@ -1,6 +1,4 @@
 // REQUIRES: system-linux
----------------
arichardson wrote:

Unrelated, but I don't see why this would fail on e.g. a FreeBSD host. Maybe it should be !WINDOWS? Although that should also be handled by REQUIRES: shell

https://github.com/llvm/llvm-project/pull/94055