glsl_type: Drop the glsl_get_array_instance C helper

It was added in bce6f99875 even though it's completely redundant with
glsl_array_type().

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

src/compiler/glsl/gl_nir_lower_samplers_as_deref.c

@@ -99,7 +99,7 @@ remove_struct_derefs_prep(nir_deref_instr **p, char **name,
 
       remove_struct_derefs_prep(&p[1], name, location, type);
 
-      *type = glsl_get_array_instance(*type, length);
+      *type = glsl_array_type(*type, length);
       break;
    }