QmlDesigner: Fix for Connections visibility

- Fixes an issue with connection model not finding Connections in 5.15

Task: QDS-2412

Change-Id: I07bbb900907aaaebccdd90dbc1f037ee0b2fcc61
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/components/connectioneditor/connectionmodel.cpp

@@ -56,7 +56,8 @@ bool isConnection(const QmlDesigner::ModelNode &modelNode)
 {
     return (modelNode.type() == "Connections"
             || modelNode.type() == "QtQuick.Connections"
-            || modelNode.type() == "Qt.Connections");
+            || modelNode.type() == "Qt.Connections"
+            || modelNode.type() == "QtQml.Connections");
 
 }