Remove outdated comment and unnecessary initialization call

In construction of QPropertyBindingPrivate was an initialization
of inlineDependencyObservers with a comment that this is necessary
because of a union. But inlineDependencyObservers is not inside a
union. The comment is outdated and the explicit initialization
superfluous. This patch removes it.

Change-Id: I06544a816533c41af8fc5da3ef44ddd7c18ca86e
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/kernel/qproperty_p.h

@@ -235,7 +235,6 @@ public:
         , eagerlyUpdating(false)
         , isQQmlPropertyBinding(isQQmlPropertyBinding)
         , vtable(vtable)
-        , inlineDependencyObservers() // Explicit initialization required because of union
         , location(location)
         , metaType(metaType)
     {}