Gitlab ci `!reference` in cache is not validating correctly anymore

Since the new update , for this code:

  cache:
    - paths:
        - ${PIP_CACHE_DIR}
      key:
        prefix: "pip-${PYTHON_VERSION}-${CI_JOB_NAME}-${TOX_VERSION}"
        files:
          - requirements.txt
    - !reference [ .apt:cache, cache ]

I'm getting this error:

  .gitlab-ci.yml::$.test.cache: [{'paths': ['${PIP_CACHE_DIR}'], 'key': {'prefix': 'pip-${PYTHON_VERSION}-${CI_JOB_NAME}-${TOX_VERSION}', 'files': ['requirements.txt']}}, ['.apt:cache', 'cache']] is not valid under any of the given schemas
  Underlying errors caused this.

  Best Match:
    $.test.cache: [{'paths': ['${PIP_CACHE_DIR}'], 'key': {'prefix': 'pip-${PYTHON_VERSION}-${CI_JOB_NAME}-${TOX_VERSION}', 'files': ['requirements.txt']}}, ['.apt:cache', 'cache']] is not of type 'object'
  Best Deep Match:
    $.test.cache[1]: ['.apt:cache', 'cache'] is not of type 'object'

Start by reproducing the validation error with the GitLab CI YAML shown in the issue, then trace the GitLab CI schema validation path. Done means the cache entry using !reference [ .apt:cache, cache ] is accepted correctly and the regression is covered by a test.