CppEditorOutline: Remove unused method

Remove also unused include and forward declaration.

Change-Id: I67d9ea45bc1073653b17faa3433f132a5e43f924
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/cppeditor/cppeditoroutline.cpp

@@ -150,12 +150,6 @@ QWidget *CppEditorOutline::widget() const
     return m_combo;
 }
 
-QSharedPointer<CPlusPlus::Document> getDocument(const Utils::FilePath &filePath)
-{
-    const CPlusPlus::Snapshot snapshot = CppModelManager::snapshot();
-    return snapshot.document(filePath);
-}
-
 void CppEditorOutline::updateNow()
 {
     m_combo->view()->expandAll();

src/plugins/cppeditor/cppeditoroutline.h

@@ -5,7 +5,6 @@
 
 #include "cppoutlinemodel.h"
 
-#include <QModelIndex>
 #include <QObject>
 
 #include <memory>
@@ -16,7 +15,6 @@ class QSortFilterProxyModel;
 class QTimer;
 QT_END_NAMESPACE
 
-namespace TextEditor { class TextEditorWidget; }
 namespace Utils { class TreeViewComboBox; }
 
 namespace CppEditor {