rust: document `bindgen` 0.71.0 regression

rust: document `bindgen` 0.71.0 regression

`bindgen` 0.71.0 regressed [1] on the "`--version` requires header"
issue which appeared in 0.69.0 first [2] and was fixed in 0.69.1. It
has been fixed again in 0.71.1 [3].

Thus document it so that, when we upgrade the minimum past 0.69.0 in the
future, we do not forget that we cannot remove the workaround until we
arrive at 0.71.1 at least.

Link: https://github.com/rust-lang/rust-bindgen/issues/3039
Link: https://github.com/rust-lang/rust-bindgen/issues/2677
Link: https://github.com/rust-lang/rust-bindgen/blob/main/CHANGELOG.md#v0711-2024-12-09
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241209212544.1977065-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>