ci: fix the opem test rule (wrt opam depext)

.gitlab-ci.yml

@@ -39,7 +39,7 @@ test_opam_test:
   script:
     - opam repo add verimag-sync-repo "http://www-verimag.imag.fr/DIST-TOOLS/SYNCHRONE/test/opam-repository"
     - eval `opam config env`
-    - sudo opam depext -y sasa
+    - sudo opam depext -y sasa || echo "not needed for recent opam version"
     - opam install -y sasa
   allow_failure: true
   only: