Update compiler/rustc_mir_transform/src/simplify.rs

Author: wesleywiser

compiler/rustc_mir_transform/src/simplify.rs

@@ -28,7 +28,7 @@
 //! return.
 
 use crate::MirPass;
-use rustc_data_structures::stable_set::FxHashSet;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_middle::mir::coverage::*;
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};