Stop ignoring miri leaks

Now that rust-lang/miri#940 has been fixed,
and has landed in nightly
(rust-lang/rust#70897), we should be able to run
miri with leak check enabled again!

Author: jonhoo

azure-pipelines.yml

@@ -57,11 +57,7 @@ jobs:
            - miri
      - script: cargo miri setup
        displayName: cargo miri setup
-     # ignore leaks due to
-     # https://github.com/crossbeam-rs/crossbeam/issues/464
-     # which is
-     # https://github.com/rust-lang/miri/issues/940
-     - script: cargo miri -Zmiri-ignore-leaks test
+     - script: cargo miri test
        displayName: cargo miri test
  - job: asan
    dependsOn: deny