Mesh: modernize C++: use equals default

src/Mod/Mesh/App/Core/MeshIO.cpp

@@ -3098,10 +3098,6 @@ MeshCleanup::MeshCleanup(MeshPointArray& p, MeshFacetArray& f)
 {
 }
 
-MeshCleanup::~MeshCleanup()
-{
-}
-
 void MeshCleanup::SetMaterial(Material* mat)
 {
     materialArray = mat;
@@ -3228,10 +3224,6 @@ MeshPointFacetAdjacency::MeshPointFacetAdjacency(std::size_t p, MeshFacetArray&
     Build();
 }
 
-MeshPointFacetAdjacency::~MeshPointFacetAdjacency()
-{
-}
-
 void MeshPointFacetAdjacency::Build()
 {
     std::vector<std::size_t> numFacetAdjacency(numPoints);