chore: crypto-ffi: silence warning about unexpected cfg in wasm-bindgen

(cherry picked from commit e6d3e90)

crypto-ffi/Cargo.toml

@@ -69,3 +69,6 @@ wasm-opt = false
 
 [package.metadata.wasm-pack.profile.release]
 wasm-opt = ["-Os", "--enable-mutable-globals", "--enable-threads", "--detect-features"]
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(wasm_bindgen_unstable_test_coverage)'] }