Undefine T_DATA allocators for Ruby 3.2 compatibility

[casperisfine]

Ref: https://bugs.ruby-lang.org/issues/18007

cc @tenderlove

lib/mysql2/em.rb:17: warning: undefining the allocator of T_DATA class Mysql2::Result
spec/mysql2/statement_spec.rb:56: warning: undefining the allocator of T_DATA class Mysql2::Statement

[sodabrew]

This appears to be fully backwards-compatible to earlier versions of Ruby as well?

LGTM, can merge today if you don't have any further changes to propose.

[casperisfine]

This appears to be fully backwards-compatible to earlier versions of Ruby as well?

Yes, this isn't a new API, it just start to be slowly enforced.

if you don't have any further changes to propose.

Nope all good for me.