Remove unused lockfree dependency

[jayvdb]

What does this PR do?

Removes unused dependency lockfree

Motivation

See issue

Related issues

Closes https://github.com/DataDog/glommio/issues/677

Additional Notes

Checklist

[] I have added unit tests to the code I am submitting [] My unit tests cover both failure and success scenarios [] If applicable, I have discussed my architecture

[jayvdb]

@HippoBaro see https://github.com/rustsec/advisory-db/pull/2461