Remove unnecessary class member

It's never used or accessed. It's not part of exported API.

Change-Id: Ie60a560fb6f1315a53442f3c067363e651b80768
Reviewed-by: David Edmundson <davidedmundson@kde.org>

src/plugins/platforminputcontexts/compose/qcomposeplatforminputcontext.h

@@ -74,7 +74,6 @@ protected:
 
 private:
     bool m_initialized = false;
-    xkb_context *m_context = nullptr;
     xkb_compose_table *m_composeTable = nullptr;
     xkb_compose_state *m_composeState = nullptr;
     QObject *m_focusObject = nullptr;