ci(rust): work-around false-positive lint error on Rust 1.84+

It shows

    error: unexpected `cfg` condition value: `gil-refs`

during clippy execution

The error is due to a new lint turned on on Rust 1.84 which trips
older PyO3 code. It'll go away when upgrading to 0.23[^1], but it needs
API changes, so for the time being the lint is disabled instead.

[^1]: PyO3/pyo3#4743

rust/Cargo.toml

@@ -31,3 +31,7 @@ rand = "0.8.4"
 [[bench]]
 harness = false
 name = "benches_main"
+
+[lints.rust]
+# Required for Rust >= 1.84 && pyo3 < 0.23
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(addr_of)'] }