Avoid retriggering the completion box when it's already there

There should be no need for the text editor to request an update of the
completion box, since when it's there it will have focus and update
itself.

Reviewed-by: Roberto Raggi

src/plugins/texteditor/basetexteditor.cpp

@@ -1415,6 +1415,9 @@ void BaseTextEditor::_q_requestAutoCompletion()
 {
     d->m_requestAutoCompletionTimer->stop();
 
+    if (CompletionSupport::instance()->isActive())
+        return;
+
     if (d->m_requestAutoCompletionRevision == document()->revision() &&
             d->m_requestAutoCompletionPosition == position())
         emit requestAutoCompletion(editableInterface(), false);