As a temporary measure while a proper fix for
`tests/ui/sized-hierarchy/incomplete-inference-issue-143992.rs`
is implemented, make `MetaSized` obligations always hold. In effect,
temporarily reverting the `sized_hierarchy` feature. This is a small
change that can be backported.
This test case is a reduction from the `hwc` crate on GitHub, following a
crater run. It passes with the next solver but fails on the current
solver due to a known limitation of the current solver. It starts fails
on the current solver with the `sized_hierarchy` changes because `?Sized`
is now a proper bound.
