Arrow2 allows double free in `safe` code

The struct Ffi_ArrowArray implements #derive(Clone) that is inconsistent with its custom implementation of Drop, resulting in a double free when cloned.

Cloning this struct in safe results in a segmentation fault, which is unsound.

This derive was removed from this struct. All users are advised to either:

• bump the patch version of this crate (for versions v0.7,v0.8,v0.9), or
• migrate to a more recent version of the crate (when using <0.7).

Doing so elimitates this vulnerability (code no longer compiles).