Avoid using implicit assignment operator in wxAny test

This implicitly declared operator is deprecated because MyClass has an
explicitly defined copy ctor, so we either need to define the assignment
explicitly too or just not use it at all, as done by this commit.

tests/any/anytest.cpp

@@ -479,8 +479,8 @@ class wxMyVariantData : public wxVariantData
 {
 public:
     wxMyVariantData(const MyClass& value)
+        : m_value(value)
     {
-        m_value = value;
     }
 
     virtual bool Eq(wxVariantData& WXUNUSED(data)) const override