threadshare: Fix some new clippy beta warnings

warning: this expression borrows a value the compiler would automatically borrow --> generic/threadshare/src/runtime/executor/async_wrapper.rs:402:19 | 402 | match (&mut *self).get_mut().read(buf) { | ^^^^^^^^^^^^ help: change this to: (*self) | = note: #[warn(clippy::needless_borrow)] on by default = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow