[clang] [Clang][OpenMP] Fix `if` clause not affecting `teams` construct on host (PR #207444)

[Jan André Reuter via cfe-commits]

Thyre wrote:

> Commit message is incorrect: "if present and true, emit __kmpc_push_num_teams with teams set to 1." Code does the opposite: SerialLeague runs on the false branch. Also references __kmpc_push_num_threads instead of __kmpc_push_num_teams.

Thanks a lot for noticing. I adapted the commit message and PR description accordingly.
It should now consistently mention `__kmpc_push_num_teams` instead of `[...]_num_threads`.
I also replaced the `if present and true` by `if present and false`.

https://github.com/llvm/llvm-project/pull/207444