CI: also use ssreflect dev

.gitlab-ci.yml

@@ -44,6 +44,6 @@ build-coq.8.6.1:
 build-iris.dev:
   <<: *template
   variables:
-    OPAM_PINS: "coq version dev   coq-mathcomp-ssreflect version 1.6.4   coq-iris.dev git https://gitlab.mpi-sws.org/FP/iris-coq.git#$IRIS_REV"
+    OPAM_PINS: "coq version dev   coq-mathcomp-ssreflect version dev   coq-iris.dev git https://gitlab.mpi-sws.org/FP/iris-coq.git#$IRIS_REV"
   only:
   - triggers