Keep readonly qualifier

Let's not reformat readonly qualifiers away. They are likely there for a
reason.

Task-number: QTCREATORBUG-15745
Change-Id: Iaab7a8edb47fccd0cf36759750500a93be45bbc2
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>
Reviewed-by: Marco Benelli <marco.benelli@theqtcompany.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/qmljs/qmljsreformatter.cpp

@@ -533,6 +533,8 @@ protected:
         if (ast->type == UiPublicMember::Property) {
             if (ast->isDefaultMember)
                 out("default ", ast->defaultToken);
+            else if (ast->isReadonlyMember)
+                out("readonly ", ast->readonlyToken);
             out("property ", ast->propertyToken);
             if (!ast->typeModifier.isNull()) {
                 out(ast->typeModifierToken);