QStringView: remove pointless Q_ASSERT in toString()

QString and QStringView have the same size_type these days.

Pick-to: 6.5 6.4
Change-Id: I59ffe78f51e06ccc130562b1682fb4a672c3ec22
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/text/qstring.h

@@ -899,7 +899,7 @@ QString QLatin1StringView::toString() const { return *this; }
 //
 
 QString QStringView::toString() const
-{ return Q_ASSERT(size() == size()), QString(data(), size()); }
+{ return QString(data(), size()); }
 
 qint64 QStringView::toLongLong(bool *ok, int base) const
 { return QString::toIntegral_helper<qint64>(*this, ok, base); }