[Test] Fix a test to be valid

OpenMP 5.2 restriction: Each list item must have C_PTR or Cray pointer type or have the POINTER or ALLOCATABLE attribute.

Author: Thirumalai-Shaktivel

flang/test/Examples/omp-declarative-directive.f90

@@ -7,7 +7,7 @@
 ! 2.8.2 declare-simd
 
 subroutine declare_simd_1(a, b)
-  real(8), intent(inout) :: a, b
+  real(8), intent(inout), allocatable :: a, b
   !$omp declare simd(declare_simd_1) aligned(a)
   a = 3.14 + b
 end subroutine declare_simd_1