Reformat more code to one import per line

Summary:
`./test.py --rustfmt-only` does not reformat these (don't know why).

This is preparation to reformat whole fbsource.

```
find fbcode/buck2 -name '*.rs' | xargs arc rustfmt --config group_imports=StdExternalCrate,imports_granularity=Item
```

Reviewed By: ndmitchell

Differential Revision: D37524079

fbshipit-source-id: 1087335107e0f722d47abcced4056338d49b3d54

Author: stepancheg

linter_test/src/lib.rs

@@ -17,7 +17,8 @@
 #![plugin(gazebo_lint)]
 #![allow(unused)] // Unused because these are gazebo_lint test cases with no actual use
 
-use std::{collections::HashSet, sync::Arc};
+use std::collections::HashSet;
+use std::sync::Arc;
 
 use gazebo::prelude::*;
 
@@ -362,7 +363,9 @@ mod impl_dupe_warm {
 }
 
 mod should_warn {
-    use anyhow::{Error, Result, *};
+    use anyhow::Error;
+    use anyhow::Result;
+    use anyhow::*;
 }
 
 fn uses_bail() -> anyhow::Result<()> {