QXmlString::size(): Change return type to qsizetype

Task-number: QTBUG-86224
Change-Id: I32baa08d2d116d7d81ba980d077f2e144a23b966
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/serialization/qxmlstream.h

@@ -67,7 +67,7 @@ public:
     }
 
     inline operator QStringView() const { return QStringView(m_string.data(), m_string.size); }
-    inline int size() const { return m_string.size; }
+    inline qsizetype size() const { return m_string.size; }
 };
 
 }