TextEditor: Reset mimetype after open() in all BaseTextEditors

This was already done in all major editors and should not harm
all others.

Change-Id: I7e19d285c4b85419a9a1f9afa961addecf682eaf
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/cppeditor/cppeditor.cpp

@@ -546,14 +546,6 @@ void CppEditorWidget::keyPressEvent(QKeyEvent *e)
     TextEditor::BaseTextEditorWidget::keyPressEvent(e);
 }
 
-bool CppEditor::open(QString *errorString, const QString &fileName, const QString &realFileName)
-{
-    if (!TextEditor::BaseTextEditor::open(errorString, fileName, realFileName))
-        return false;
-    textDocument()->setMimeType(Core::MimeDatabase::findByFile(QFileInfo(fileName)).type());
-    return true;
-}
-
 void CppEditorWidget::applyFontSettings()
 {
     // This also makes the document apply font settings