Editor: accept drop actions

In order to remove the selected text of another editor widget when
dragging text from one editor to another the drop event needs to be
accepted.

Fixes: QTCREATORBUG-28125
Change-Id: I8333fe096baf589e5669fc43370fc3519c72bb2d
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/texteditor/texteditor.cpp

@@ -7678,6 +7678,7 @@ void TextEditorWidget::dropEvent(QDropEvent *e)
     insertFromMimeData(mime);
     delete mimeOverwrite;
     cursor.endEditBlock();
+    e->acceptProposedAction();
 }
 
 QMimeData *TextEditorWidget::duplicateMimeData(const QMimeData *source)