[flang][OpenMP] Add private to allocate in parallel-sections.f90 (#92185)

Add a privatizing clause to the construct that uses `allocate` clause.
Amend the CHECK lines to reflect the expected output.

Author: kparzysz

flang/test/Lower/OpenMP/parallel-sections.f90

@@ -39,13 +39,10 @@ end subroutine omp_parallel_sections
 subroutine omp_parallel_sections_allocate(x, y)
   use omp_lib
   integer, intent(inout) :: x, y
+  !CHECK: omp.parallel
   !CHECK: %[[allocator_1:.*]] = arith.constant 4 : i64
-  !CHECK: %[[allocator_2:.*]] = arith.constant 4 : i64
-  !CHECK: omp.parallel allocate(
-  !CHECK: %[[allocator_2]] : i64 -> %{{.*}} : !fir.ref<i32>) {
-  !CHECK: omp.sections allocate(
-  !CHECK: %[[allocator_1]] : i64 -> %{{.*}} : !fir.ref<i32>) {
-  !$omp parallel sections allocate(omp_high_bw_mem_alloc: x)
+  !CHECK: omp.sections allocate(%[[allocator_1]] : i64 -> %{{.*}} : !fir.ref<i32>) {
+  !$omp parallel sections allocate(omp_high_bw_mem_alloc: x) private(x, y)
     !CHECK: omp.section {
     !$omp section
       x = x + 12