Proptest with Rust 1.72 produces clippy::arc_with_non_send_sync warnings

[sunshowers]

The warnings appear to be because we generate Arc<BoxedStrategy<T>> sometimes, and come from the following places that I could see:

• [x] The prop_oneof! macro: https://github.com/proptest-rs/proptest/pull/363
• [x] proptest-derive: https://github.com/proptest-rs/proptest/pull/365

[matthew-russo]

363 and #365 merged. Thanks!