EditorManager: Remove QString openEditor(At) overloads

In favor of the FilePath/Link ones.

Change-Id: I5caf9e0f8de304ff4ee12329557aa50a6f3a0c69
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/cppeditor/cppcompletion_test.cpp

@@ -79,7 +79,7 @@ public:
         QVERIFY(!fileName.isEmpty());
 
         // Open in editor
-        m_editor = EditorManager::openEditor(fileName);
+        m_editor = EditorManager::openEditor(Utils::FilePath::fromString(fileName));
         QVERIFY(m_editor);
         closeEditorAtEndOfTestCase(m_editor);
         m_editorWidget = TextEditorWidget::fromEditor(m_editor);