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_graphviz/src/lib.rs

@@ -279,12 +279,12 @@
 #![feature(rustdoc_internals)]
 // tidy-alphabetical-end
 
-use LabelText::*;
-
 use std::borrow::Cow;
 use std::io;
 use std::io::prelude::*;
 
+use LabelText::*;
+
 /// The text for a graphviz label on a node or edge.
 pub enum LabelText<'a> {
     /// This kind of label preserves the text directly as is.