update to Coq 8.18

Let's see if we get any warnings.

.gitlab-ci.yml

@@ -28,11 +28,11 @@ variables:
 
 ## Build jobs
 
-build-coq.8.17.0:
+build-coq.8.18.0:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.17.0"
-    DENY_WARNINGS: "1"
+    OPAM_PINS: "coq version 8.18.0"
+    # DENY_WARNINGS: "1"
     MANGLE_NAMES: "1"
   tags:
   - fp-timing
@@ -40,7 +40,7 @@ build-coq.8.17.0:
 trigger-iris.timing:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.17.0   git+https://gitlab.mpi-sws.org/$IRIS_REPO#$IRIS_REV"
+    OPAM_PINS: "coq version 8.18.0   git+https://gitlab.mpi-sws.org/$IRIS_REPO#$IRIS_REV"
   tags:
   - fp-timing
   only: