nir: Don't set dest in SSBO store glsl_to_nir conversion

This matches the function signature created in
lower_ubo_reference_visitor::ssbo_store which has a void return.

Suggested-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>

src/glsl/nir/glsl_to_nir.cpp

@@ -800,7 +800,6 @@ nir_visitor::visit(ir_call *ir)
             instr = nir_intrinsic_instr_create(shader, op);
             instr->src[2] = evaluate_rvalue(offset);
             instr->const_index[0] = 0;
-            dest = &instr->dest;
          } else {
             instr->const_index[0] = const_offset->value.u[0];
          }