TextEditor: Remove unneeded code

There is no need to trigger the automatic proposal timer anymore. This
was added to fix QTCREATORBUG-6052.

The removed code resulted in 3 completion requests when triggering a
function call: foo(. One is sufficient.

Change-Id: I3da6574bddaaaa101145ea607483e83620110c5f
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/texteditor/codeassist/codeassistant.cpp

@@ -441,8 +441,6 @@ void CodeAssistantPrivate::notifyChange()
             m_proposalWidget->updateProposal(
                 m_editorWidget->textAt(m_proposal->basePosition(),
                                      m_editorWidget->position() - m_proposal->basePosition()));
-            if (m_proposal->isFragile())
-                startAutomaticProposalTimer();
         }
     }
 }