QVariant: visually separate PrivateShared and Private nested classes

Add an empty line between the two.

Pick-to: 6.5
Change-Id: If1c50ebb0b825acc53364cce2e083332367e757c
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/kernel/qvariant.h

@@ -89,6 +89,7 @@ public:
         const void *data() const { return reinterpret_cast<const uchar *>(this) + offset; }
         void *data() { return reinterpret_cast<uchar *>(this) + offset; }
     };
+
     struct Private
     {
         static constexpr size_t MaxInternalSize = 3 * sizeof(void *);