Fix #136422: Workbench: Missing shadows for backface culled non-manifold meshes

Regression caused by 20d09435ab.
Ensure compute_visibility runs again after updating the mode.

Pull Request: https://projects.blender.org/blender/blender/pulls/136507

source/blender/draw/engines/workbench/workbench_shadow.cc

@@ -206,6 +206,8 @@ bool ShadowPass::ShadowView::debug_object_culling(Object *ob)
 void ShadowPass::ShadowView::set_mode(ShadowPass::PassType type)
 {
   current_pass_type_ = type;
+  /* Ensure compute_visibility runs again after updating the mode. */
+  manager_fingerprint_ = 0;
 }
 
 void ShadowPass::ShadowView::compute_visibility(ObjectBoundsBuf &bounds,