Remove unused currentVariant in 3D renderers

The currentVariant variable was only used for the DNP condition
that was removed in commit 40205eb181. Remove the now-unused
declarations to fix -Wunused-variable warnings.

3d-viewer/3d_rendering/opengl/render_3d_opengl.cpp

@@ -1047,7 +1047,6 @@ void RENDER_3D_OPENGL::get3dModelsSelected( std::list<MODELTORENDER> &aDstRender
         return;
 
     EDA_3D_VIEWER_SETTINGS::RENDER_SETTINGS& cfg = m_boardAdapter.m_Cfg->m_Render;
-    const wxString currentVariant = m_boardAdapter.GetBoard()->GetCurrentVariant();
 
     // Go for all footprints
     for( FOOTPRINT* fp : m_boardAdapter.GetBoard()->Footprints() )

3d-viewer/3d_rendering/raytracing/create_scene.cpp

@@ -1925,8 +1925,6 @@ void RENDER_3D_RAYTRACE_BASE::load3DModels( CONTAINER_3D& aDstContainer,
         return;
     }
 
-    const wxString currentVariant = m_boardAdapter.GetBoard()->GetCurrentVariant();
-
     // Go for all footprints
     for( FOOTPRINT* fp : m_boardAdapter.GetBoard()->Footprints() )
     {