QmlJSEditor: do not wait for the semantic info update

... when destructing a qmljseditor. Just let the updater continue and
delete it once it finishes.

Fixes: QTCREATORBUG-28206
Change-Id: Icabe10f17b7bf326bb15e5ee622504c477d83acf
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/plugins/qmljseditor/qmljssemanticinfoupdater.cpp

@@ -19,11 +19,7 @@
 namespace QmlJSEditor {
 namespace Internal {
 
-SemanticInfoUpdater::SemanticInfoUpdater(QObject *parent)
-        : QThread(parent)
-        , m_wasCancelled(false)
-{
-}
+SemanticInfoUpdater::SemanticInfoUpdater() = default;
 
 SemanticInfoUpdater::~SemanticInfoUpdater() = default;