Remove QVariant(QDataStream) constructor

The constructor wasn't constructing a QVariant holding a
QDataStream, bug loading the variant from the datastream.

This is opposed to how QDataStream works in all other places,
and also not in line with all other constructors for QVariant.

[ChangeLog][QtCore][QVariant] Removed the QVariant(QDataStream)
constructor. Use QVariant().load(datastream) instead.

Change-Id: I6ac54e12166b9383c09c3940eef2516f896fd359
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qvariant.cpp

@@ -538,17 +538,6 @@ QVariant::QVariant(const QVariant &p)
         t.construct(&d, p.constData());
 }
 
-#ifndef QT_NO_DATASTREAM
-/*!
-    Reads the variant from the data stream, \a s.
-*/
-QVariant::QVariant(QDataStream &s)
-{
-    d.is_null = true;
-    s >> *this;
-}
-#endif //QT_NO_DATASTREAM
-
 /*!
   \fn QVariant::QVariant(const QString &val)
 

src/corelib/kernel/qvariant.h

@@ -177,10 +177,6 @@ class Q_CORE_EXPORT QVariant
     explicit QVariant(QMetaType type, const void *copy = nullptr);
     QVariant(const QVariant &other);
 
-#ifndef QT_NO_DATASTREAM
-    explicit QVariant(QDataStream &s);
-#endif
-
     QVariant(int i);
     QVariant(uint ui);
     QVariant(qlonglong ll);