[UR][CUDA] Fix command-buffer handle inheritance

The `ur_exp_command_buffer_handle_t_` definition in the CUDA
adapter was missed in intel#17118 in
the changes to inherit from a base handle.

Discovered by seeing segfaults in the UR CTS tests locally, and
git bisecting back to that change.

Author: EwanC

unified-runtime/source/adapters/cuda/command_buffer.hpp

@@ -128,7 +128,7 @@ struct ur_exp_command_buffer_command_handle_t_ : ur::cuda::handle_base {
   command_data_type_t CommandData;
 };
 
-struct ur_exp_command_buffer_handle_t_ {
+struct ur_exp_command_buffer_handle_t_ : ur::cuda::handle_base {
 
   ur_exp_command_buffer_handle_t_(ur_context_handle_t Context,
                                   ur_device_handle_t Device, bool IsUpdatable);