[clang] [OpenMP] Remove complex reduction variable support (PR #82497)

[Alexey Bataev via cfe-commits]

alexey-bataev wrote:

> @alexey-bataev do you have any concerns about removing this case?

I think better to add a test for complex reductions rather than removing its support. This simple test fails without complex supports.
```
#include <complex.h>
int foo() {
  int i;
  int j;
  complex float sum;

  #pragma omp target teams loop reduction(+:sum) collapse(2) \
      bind(parallel) order(concurrent) lastprivate(j) map(tofrom:sum)
  for(i=0; i<10; i++)
    for(j=0; j<10; j++)
      sum += i;

  return 0;
}
```

https://github.com/llvm/llvm-project/pull/82497