Auto merge of #806 - varkor:patch-1, r=RalfJung
Auto merge of #806 - varkor:patch-1, r=RalfJung

Fix `unused_must_use` inside `Box`

After https://github.com/rust-lang/rust/pull/62228, this will be linted against (and causes the test to fail). (This blocks https://github.com/rust-lang/rust/pull/62228.)

rust-lang/miri,rust-lang/miri,tsion/miri,rust-lang/miri,rust-lang/miri