[llvm-branch-commits] [clang] Remove shell requirements from tests (PR #156905)

[Aiden Grossman via llvm-branch-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/156905

Most of these tests do not actually have a shell requirement. The shell
requirement ended up in the test either from cargo culting (from what I
can tell) or because the test authors actually meant to mark Windows as
unsupported. This prevents enablement of lit's internal shell within
clang.

Towards #102699.