Auto merge of #4909 - zackmdavis:tidy_paren, r=matklad

unblock rust-lang/rust#46980 by cleaning up an unused pair of parentheses

While this might seem like too trivial of a stylistic nitpick to deserve
its own commit, this [is needed to unblock](rust-lang/rust#46980 (comment)) the PR rust-lang/rust#46980 (which makes
the unused-parens lint look at function arguments, which it previously didn't).

Author: bors

src/cargo/ops/cargo_test.rs

@@ -120,7 +120,7 @@ fn run_unit_tests(options: &TestOptions,
         let (kind, test, e) = errors.pop().unwrap();
         Ok((Test::UnitTest(kind, test), vec![e]))
     } else {
-        Ok((Test::Multiple, errors.into_iter().map((|(_, _, e)| e)).collect()))
+        Ok((Test::Multiple, errors.into_iter().map(|(_, _, e)| e).collect()))
     }
 }