Fix memoizable insertion to preserve freezer option

[mbj]

Mutant is right now configured to detect and re-produce memoized methods via the memoziable gem. In case the memoizable is used with adamantium the additional freezer option is currently silently dropped.

Resulting in an unintend behavior change observable in some noop failures. While certainly an interesting mutation, this mutation should be inserted explicitly, but not inside the noops.