Prepare for rustfmt 2.0

Summary:
Generated by formatting with rustfmt 2.0.0-rc.2 and then a second time with fbsource's current rustfmt (1.4.14).

This results in formatting for which rustfmt 1.4 is idempotent but is closer to the style of rustfmt 2.0, reducing the amount of code that will need to change atomically in that upgrade.

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*Why now?* **:** The 1.x branch is no longer being developed and fixes like https://github.com/rust-lang/rustfmt/issues/4159 (which we need in fbcode) only land to the 2.0 branch.

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Reviewed By: zertosh

Differential Revision: D23568784

fbshipit-source-id: 7401066bfc99390686eb3fd9dc6f9888ccef9487

packer/src/main.rs

@@ -313,7 +313,10 @@ mod test {
 
         let manifest_content = std::fs::read_to_string(&path)?;
 
-        assert_eq!(manifest_content, "{\n  \"files\": {\n    \"core\": \"f4bb1975bf1f81f76ce824f7536c1e101a8060a632a52289d530a6f600d52c92\"\n  }\n}");
+        assert_eq!(
+            manifest_content,
+            "{\n  \"files\": {\n    \"core\": \"f4bb1975bf1f81f76ce824f7536c1e101a8060a632a52289d530a6f600d52c92\"\n  }\n}"
+        );
 
         Ok(())
     }