fix(deps): update rust crate lru to 0.18

Author: renovate[bot]

crates/flagd/Cargo.toml

@@ -54,7 +54,7 @@ async-trait = { workspace = true }
 tokio = { workspace = true }
 serde_json = { workspace = true }
 serde = { workspace = true }
-lru = "0.16"
+lru = "0.18"
 tokio-stream = "0.1"
 tracing = { workspace = true }
 thiserror = { workspace = true }