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

[Aaron Ballman via llvm-commits]

AaronBallman wrote:

I do not think Flang is in a state where it makes sense to precommit test Flang because of changes to Clang or LLVM for any platform. At least within Clang, I'm unaware of precommit CI ever testing a change to Clang which catches a legitimate failure in Flang, but there have been plenty of instances of Flang being in an invalid state and causing precommit CI to "fail" for Clang reviews as a result.

That said, I think it makes a lot of sense for Flang to have precommit CI testing when Flang source changes.

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