doc/tutorial: field where of struct starpu_codelet is optional, no longer set it

doc/tutorial/hello_world.c

@@ -32,7 +32,6 @@ void cpu_func(void *buffers[], void *cl_arg)
 
 struct starpu_codelet cl =
 {
-    .where = STARPU_CPU,
     .cpu_funcs = {cpu_func, NULL},
     .nbuffers = 0
 };

doc/tutorial/vector_scal.c

@@ -31,7 +31,6 @@ extern void scal_cuda_func(void *buffers[], void *_args);
 extern void scal_opencl_func(void *buffers[], void *_args);
 
 static struct starpu_codelet cl = {
-    .where = STARPU_CPU | STARPU_CUDA | STARPU_OPENCL,
     /* CPU implementation of the codelet */
     .cpu_funcs = {scal_cpu_func, NULL},
 #ifdef STARPU_USE_CUDA