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_fs_util/src/lib.rs

@@ -1,7 +1,6 @@
 use std::ffi::CString;
-use std::fs;
-use std::io;
 use std::path::{absolute, Path, PathBuf};
+use std::{fs, io};
 
 // Unfortunately, on windows, it looks like msvcrt.dll is silently translating
 // verbatim paths under the hood to non-verbatim paths! This manifests itself as