QVariant: visually separate PrivateShared and Private nested classes

Add an empty line between the two.

Change-Id: If1c50ebb0b825acc53364cce2e083332367e757c
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 7041d9dd7518ae37a0067e702f6fc1d88506395d)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/kernel/qvariant.h

@@ -72,6 +72,7 @@ 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 *);