TextEditor: Move CompletionAssistProvider construction

... to the editor factories and pass it to the document, not the widget.
Saves some code, puts fewer objects into the object pool.

Change-Id: Iaaf250af74dc4e0c62700873accbb40ba88b7d9e
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: David Schulz <david.schulz@digia.com>

src/plugins/qmljseditor/qmljseditorplugin.cpp

@@ -40,7 +40,6 @@
 #include "qmltaskmanager.h"
 #include "quicktoolbar.h"
 #include "quicktoolbarsettingspage.h"
-#include "qmljscompletionassist.h"
 #include "qmljsquickfixassist.h"
 
 #include <qmljs/qmljsicons.h>
@@ -209,7 +208,6 @@ bool QmlJSEditorPlugin::initialize(const QStringList & /*arguments*/, QString *e
 
     m_quickFixAssistProvider = new QmlJSQuickFixAssistProvider;
     addAutoReleasedObject(m_quickFixAssistProvider);
-    addAutoReleasedObject(new QmlJSCompletionAssistProvider);
 
     errorMessage->clear();