radv: Stop updating the stack_size in insert_rt_case

There are two paths that call insert_rt_case:
- Traversal shader: The stack size is ignored.
- Monolithic raygen shader: The stack sizes of the inlined shaders are
                            accounted for in compute_rt_stack_size.

Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24809>

src/amd/vulkan/radv_rt_shader.c

@@ -787,8 +787,6 @@ insert_rt_case(nir_builder *b, nir_shader *shader, struct rt_variables *vars, ni
    NIR_PASS(_, shader, nir_lower_returns);
    NIR_PASS(_, shader, nir_opt_dce);
 
-   src_vars.stack_size = MAX2(src_vars.stack_size, shader->scratch_size);
-
    inline_constants(b->shader, shader);
 
    nir_push_if(b, nir_ieq_imm(b, idx, call_idx));