QSqlQuery: remove unneeded friend tst_QSqlQuery

... as it is no longer needed.

Pick-to: 6.7
Change-Id: Ia60b6e53675260ef0e793ac1b44c913af1454b35
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

src/sql/kernel/qsqlresult.h

@@ -8,9 +8,6 @@
 #include <QtCore/qvariant.h>
 #include <QtCore/qcontainerfwd.h>
 
-// for testing:
-class tst_QSqlQuery;
-
 QT_BEGIN_NAMESPACE
 
 
@@ -26,8 +23,6 @@ class Q_SQL_EXPORT QSqlResult
     Q_DECLARE_PRIVATE(QSqlResult)
     friend class QSqlQuery;
     friend class QSqlTableModelPrivate;
-    // for testing:
-    friend class ::tst_QSqlQuery;
 
 public:
     virtual ~QSqlResult();