ci: updating clean-git-history-checking stage

Author: DeveloperC286

.gitlab-ci.yml

@@ -14,7 +14,7 @@ clean-git-history-checking:
     - cargo install clean_git_history
   script:
     # Check all the commits in the branch.
-    - /usr/local/cargo/bin/clean_git_history --from-reference "origin/$CI_MERGE_REQUEST_TARGET_BRANCH_NAME"
+    - /usr/local/cargo/bin/clean_git_history --from-reference "origin/${CI_MERGE_REQUEST_TARGET_BRANCH_NAME}"
   rules:
     - if: $CI_MERGE_REQUEST_ID