AIFS Single virtual quickstart: read the production catalog

[mrshll]

Removes the two lines that point the AIFS Single virtual quickstart at the staging catalog, so it reads the production catalog like every other quickstart.

Order

1. Merge Regenerate the AIFS Single virtual quickstart outputs against v0.2.0 #77, which this is stacked on. Until then this PR's base is Regenerate the AIFS Single virtual quickstart outputs against v0.2.0 #77's branch, so the diff here is only cell 2's source, and the notebook checks do not run, because they only trigger for pull requests that target main.
2. Merge Promote ecmwf-aifs-single-forecast-virtual (v0.2.0) to production dynamical-stac#108 and confirm the production catalog lists ecmwf-aifs-single-forecast-virtual. Before that, dynamical_catalog.open raises UnknownDatasetError here.
3. Re-run this PR's checks against production, and merge it once the notebook shard passes.

The notebook on main keeps working in the meantime, because the staging and production collections point at the same store. The stored outputs do not change for the same reason.