Update Secret-Detection template deprecated ENV ref

As of v9.0 CI_BUILD_REF_NAME is now CI_COMMIT_REF_NAME, see
https://docs.gitlab.com/ee/ci/variables/deprecated_variables.html

lib/gitlab/ci/templates/Security/Secret-Detection.gitlab-ci.yml

@@ -34,8 +34,8 @@ secret_detection:
       when: never
     - if: $CI_COMMIT_BRANCH && $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH
   script:
-    - git fetch origin $CI_DEFAULT_BRANCH $CI_BUILD_REF_NAME
-    - git log --left-right --cherry-pick --pretty=format:"%H" refs/remotes/origin/$CI_DEFAULT_BRANCH...refs/remotes/origin/$CI_BUILD_REF_NAME > "$CI_COMMIT_SHA"_commit_list.txt
+    - git fetch origin $CI_DEFAULT_BRANCH $CI_COMMIT_REF_NAME
+    - git log --left-right --cherry-pick --pretty=format:"%H" refs/remotes/origin/$CI_DEFAULT_BRANCH...refs/remotes/origin/$CI_COMMIT_REF_NAME > "$CI_COMMIT_SHA"_commit_list.txt
     - export SECRET_DETECTION_COMMITS_FILE="$CI_COMMIT_SHA"_commit_list.txt
     - /analyzer run
     - rm "$CI_COMMIT_SHA"_commit_list.txt