expr_use_visitor: Remove FIXME that is no longer needed (and in fact

causes errors, post rebase). Issue #27592 is still alive and well,
whatever it is.

Author: nikomatsakis

src/librustc/middle/expr_use_visitor.rs

@@ -274,7 +274,6 @@ impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
     pub fn new(delegate: &'d mut Delegate<'tcx>,
                typer: &'t infer::InferCtxt<'a, 'tcx>)
                -> ExprUseVisitor<'d,'t,'a,'tcx>
-        where 'tcx: 't // FIXME(#27583) workaround apparent stage0 bug
     {
         ExprUseVisitor {
             typer: typer,