Fix migration-path ci job

v9.3.0 were using gemnasium-gitlab-service which was yanked on
rubygems

Apply suggestion to .gitlab/ci/rails.gitlab-ci.yml

.gitlab/ci/rails.gitlab-ci.yml

@@ -106,7 +106,7 @@
   variables:
     SETUP_DB: "false"
   script:
-    - git fetch https://gitlab.com/gitlab-org/gitlab-ce.git v11.5.0
+    - git fetch https://gitlab.com/gitlab-org/gitlab-ee.git v11.5.0-ee
     - git checkout -f FETCH_HEAD
     - sed -i "s/gem 'oj', '~> 2.17.4'//" Gemfile
     - bundle update google-protobuf grpc