Reformat use declarations.

The previous commit updated `rustfmt.toml` appropriately. This commit is
the outcome of running `x fmt --all` with the new formatting options.

compiler/rustc_data_structures/src/sso/map.rs

@@ -1,10 +1,12 @@
-use crate::fx::FxHashMap;
-use arrayvec::ArrayVec;
-use either::Either;
 use std::fmt;
 use std::hash::Hash;
 use std::ops::Index;
 
+use arrayvec::ArrayVec;
+use either::Either;
+
+use crate::fx::FxHashMap;
+
 /// For pointer-sized arguments arrays
 /// are faster than set/map for up to 64
 /// arguments.