Fix rebase fallout

Author: oli-obk

src/librustc_mir/const_eval.rs

@@ -13,7 +13,6 @@ use rustc::mir::interpret::{ConstEvalErr, ErrorHandled, ScalarMaybeUndef};
 use rustc::mir;
 use rustc::ty::{self, Ty, TyCtxt, subst::Subst};
 use rustc::ty::layout::{self, LayoutOf, VariantIdx};
-use rustc::ty::subst::Subst;
 use rustc::traits::Reveal;
 use rustc_data_structures::fx::FxHashMap;
 use crate::interpret::eval_nullary_intrinsic;