Bump Iris version

I need this for https://github.com/coq/coq/pull/9410

Thanks!

opam

@@ -11,5 +11,5 @@ build: [make "-j%{jobs}%"]
 install: [make "install"]
 remove: [ "sh" "-c" "rm -rf '%{lib}%/coq/user-contrib/lrust'" ]
 depends: [
-  "coq-iris" { (= "dev.2019-01-30.0.5221eb39") | (= "dev") }
+  "coq-iris" { (= "dev.2019-02-03.0.5fd7dae1") | (= "dev") }
 ]