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/transitive_relation.rs

@@ -1,11 +1,13 @@
-use crate::frozen::Frozen;
-use crate::fx::{FxHashSet, FxIndexSet};
-use rustc_index::bit_set::BitMatrix;
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::mem;
 use std::ops::Deref;
 
+use rustc_index::bit_set::BitMatrix;
+
+use crate::frozen::Frozen;
+use crate::fx::{FxHashSet, FxIndexSet};
+
 #[cfg(test)]
 mod tests;