Bump Iris.

opam

@@ -9,6 +9,6 @@ build: [make "-j%{jobs}%"]
 install: [make "install"]
 remove: ["rm" "-rf" "%{lib}%/coq/user-contrib/reloc"]
 depends: [
-  "coq-iris-heap-lang" { (= "dev.2021-09-06.2.95df9887") | (= "dev") }
+  "coq-iris-heap-lang" { (= "dev.2021-12-09.1.f52f9f6a") | (= "dev") }
   "coq-autosubst" { = "dev" }
 ]

theories/typing/types.v

@@ -296,7 +296,7 @@ Proof.
     | [ H : ∀ xs ys, xs ≡ₚ ys → is_closed_expr xs _ = is_closed_expr ys _
       |- is_closed_expr _ _ = is_closed_expr _ _ ] => eapply H; eauto
     end; try done.
-  - apply bool_decide_iff. by rewrite Hxsys.
+  - apply bool_decide_ext. by rewrite Hxsys.
   - by rewrite Hxsys.
 Qed.