Fix "Header" documentation in Core plugin

Change-Id: If3cbe51b47a3acba32429894dfb5154cd573967d
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

src/plugins/coreplugin/modemanager.cpp

@@ -50,6 +50,7 @@ namespace Core {
 
 /*!
     \class Core::ModeManager
+    \inheaderfile coreplugin/modemanager.h
     \inmodule QtCreator
 
     \brief The ModeManager class implements a mode manager.