Remove unused rails5-variables

They're no longer used and have no effect

.gitlab-ci.yml

@@ -105,10 +105,6 @@ stages:
     - docker.elastic.co/elasticsearch/elasticsearch:5.6.12
 
 # END EE-only service helpers
-.rails5-variables: &rails5-variables
-  script:
-    - export RAILS5=${RAILS5}
-    - export BUNDLE_GEMFILE=${BUNDLE_GEMFILE}
 
 .rails5: &rails5
   allow_failure: true
@@ -180,7 +176,6 @@ stages:
   <<: *dedicated-runner
   <<: *except-docs-and-qa
   <<: *pull-cache
-  <<: *rails5-variables
   stage: test
   script:
     - JOB_NAME=( $CI_JOB_NAME )