Move manifest-creation CI to python3.11

[tcompa]

Ref https://github.com/fractal-analytics-platform/fractal-tasks-core/actions/runs/13664867953/job/38203996231:

ERROR: Could not find a version that satisfies the requirement ome-zarr-models (from ngio) (from versions: none)
ERROR: No matching distribution found for ome-zarr-models