go back to 8.10 branch while we investigate 8.11 failure

.gitlab-ci.yml

@@ -49,7 +49,7 @@ build-coq.8.9.0:
 build-iris.dev:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.11.dev   coq-stdpp.dev git git+https://gitlab.mpi-sws.org/iris/stdpp.git#$STDPP_REV   coq-iris.dev git git+https://gitlab.mpi-sws.org/iris/iris.git#$IRIS_REV"
+    OPAM_PINS: "coq version 8.10.dev   coq-stdpp.dev git git+https://gitlab.mpi-sws.org/iris/stdpp.git#$STDPP_REV   coq-iris.dev git git+https://gitlab.mpi-sws.org/iris/iris.git#$IRIS_REV"
   except:
   only:
   - triggers