Although a crate may happen to be compatible with multiple editions, building with the wrong
edition can - generally speaking - lead to subtle bugs.
There are no known failures in this case, but better to match the official Cargo.toml anyway.
Fixes: e28ff81869 ("meson: Add pest rust dependencies")
Reviewed-by: Christian Gmeiner <cgmeiner@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38726>
2044cf885b