Remove an unused variable in the shell.  No bug, r=themaid

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extra : rebase_source : 2793c32ddb79901439d93f19136a906c96e3371a
Bug 985687 - Remove vestigial tinyid/shortid references, as well as the field in JSPropertySpec.  Followup to bug 975069.  r=luke

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extra : rebase_source : 9e4bd270925efb155dacb91470b617f169526824