fix: upgrade lru crate to 0.16.3 (#8845)

See https://rustsec.org/advisories/RUSTSEC-2026-0002.

Though our `ratatui` fork has a transitive dep on an older version of
the `lru` crate, so to get CI green ASAP, this PR also adds an exception
to `deny.toml` for `RUSTSEC-2026-0002`, but hopefully this will be
short-lived.

codex-rs/Cargo.toml

@@ -152,7 +152,7 @@ landlock = "0.4.4"
 lazy_static = "1"
 libc = "0.2.177"
 log = "0.4"
-lru = "0.16.2"
+lru = "0.16.3"
 maplit = "1.0.2"
 mime_guess = "2.0.5"
 multimap = "0.10.0"