JQDraggableFunctionalTest >> renderContentOn: assumes Symbol equals String

[marianopeck]

As we all know, the equality between Symbol and String is one of the big difference between Smalltalk dialects. In Pharo it is true while in other dialects like GemStone or VAST, it is false. Therefore, I propose to change the line

callbackDraggable: [ :e | top := (e at: #position) at:#top. left := (e at: #position) at:#left ];

to:

callbackDraggable: [ :e | top := (e at: #position) at: 'top'. left := (e at: #position) at: 'left' ];

As the keys are originally as String, that would work in all dialects.