fix BASE lookup in cargo-check-benches

substrate/scripts/ci/gitlab/pipeline/test.yml

@@ -91,7 +91,7 @@ cargo-check-benches:
     - !reference [.pipeline-stopper-vars, script]
     # merges in the master branch on PRs
     - |
-      export BASE=$(curl -s -H "Authorization: Bearer ${GITHUB_PR_TOKEN}" https://api.github.com/repos/paritytech/substrate/pulls/${$CI_COMMIT_REF_NAME} | jq .base.ref)
+      export BASE=$(curl -s -H "Authorization: Bearer ${GITHUB_PR_TOKEN}" https://api.github.com/repos/paritytech/substrate/pulls/${CI_COMMIT_REF_NAME} | jq .base.ref)
     - if [ $CI_COMMIT_REF_NAME != "master" ]; then
       git fetch origin +${BASE}:${BASE};
       git fetch origin +$CI_COMMIT_REF_NAME:$CI_COMMIT_REF_NAME;