[clang] [Clang][OpenMP] Fix the wrong transform of `num_teams` claused introduced in #99732 (PR #102716)

[Shilei Tian via cfe-commits]

shiltian wrote:

> A test is required

I literally don't know how to test this TBH. I think our current OpenMP tests generally don't cover this at all.

https://github.com/llvm/llvm-project/pull/102716