rust: block: update `const_refs_to_static` MSRV TODO comment
`feature(const_refs_to_static)` was stabilized in Rust 1.83.0 [1].
Thus update the comment to reflect that.
Link: https://github.com/rust-lang/rust/pull/129759 [1]
Reviewed-by: Tamir Duberstein <tamird@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260405235309.418950-17-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>