[llvm] [CI] Disable flang from Windows pre-commit tests (PR #93485)

[Aaron Ballman via llvm-commits]

AaronBallman wrote:

> I propose we disable these two dependencies for now, and let them be tested in post-commit checks. I'm assuming that, when flang itself changes in a PR, it will be tested regardless of these deps.

I think this is a happy medium (Flang still gets precommit CI test coverage when Flang changes, but relies on post-commit CI test coverage when Clang, MLIR, or LLVM changes), so I'm in favor.

https://github.com/llvm/llvm-project/pull/93485