Revert "Commenting test_validity_merge for now"

This reverts commit 8991fe67

.gitlab-ci.yml

@@ -82,7 +82,7 @@ pages:
     - web
 
 # CONTINUOUS RELEASE
-.test_validity_merge:
+test_validity_merge:
   stage: test
   variables:
     GIT_SUBMODULE_STRATEGY: normal # Clone pygeodyn_data (default is none)
@@ -94,7 +94,8 @@ pages:
     - python3 pygeodyn/release/test_release.py
 
   only:
-    - merge_requests
+    refs:
+      - merge_requests
   except:
     variables:
       - $CI_MERGE_REQUEST_TITLE =~ /^WIP:/ # WILL ONLY WORK AT Gitlab 11.9