Address review comments

The following has been fixed:
- Updated comments to be `!` instead of `\\` in test file

Author: Stylie777

flang/test/Lower/OpenMP/Todo/omp-declarative-allocate.f90

@@ -5,7 +5,7 @@
 program main
   integer :: x, y
 
-  // CHECK: OpenMP directive ALLOCATE has been deprecated, please use ALLOCATORS instead.
-  // CHECK: not yet implemented: OpenMPDeclarativeAllocate
+  ! CHECK: OpenMP directive ALLOCATE has been deprecated, please use ALLOCATORS instead.
+  ! CHECK: not yet implemented: OpenMPDeclarativeAllocate
   !$omp allocate(x, y)
 end