Fix metadata persistence tests broken by f4312b3

[atoniolo76]

Commit f4312b3 broke the metadata persistence tests in contest.py by adding force=True to vol.batch_upload calls. This could have been by mistake, as it is unrelated to the Qwen-27B removal. Fixes failing test in CI.

Checklist

• Example is documented with comments throughout, in a Literate Programming style.
• Example does not require third-party dependencies to be installed locally
• Example pins its dependencies
  • Example pins container images to a stable tag, not a dynamic tag like latest
  • Example specifies a python_version for the base image, if it is used
  • Example pins all dependencies to at least minor version, ~=x.y.z or ==x.y
  • Example dependencies with version < 1 are pinned to patch version, ==0.y.z

Outside contributors

You're great! Thanks for your contribution.