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/graph/vec_graph/mod.rs

@@ -1,6 +1,7 @@
-use crate::graph::{DirectedGraph, NumEdges, Predecessors, Successors};
 use rustc_index::{Idx, IndexVec};
 
+use crate::graph::{DirectedGraph, NumEdges, Predecessors, Successors};
+
 #[cfg(test)]
 mod tests;
 

compiler/rustc_data_structures/src/graph/vec_graph/tests.rs

@@ -1,6 +1,5 @@
-use crate::graph;
-
 use super::*;
+use crate::graph;
 
 fn create_graph() -> VecGraph<usize> {
     // Create a simple graph