Clarify consolidated metadata role in minispec

[emmanuelmathot]

[emmanuelmathot]

@d-v-b Please list here all the resources we discussed during the WP1 check-in.

[d-v-b]

consolidated metadata is currently in violation of the zarr v3 spec:
see:

• zarr-python's consolidated metadata implementation violates the spec zarr-developers/zarr-specs#371
• adjust language about extra keys to permit consolidated metadata zarr-developers/zarr-specs#373
• should we remove support for inline consolidated metadata? zarr-developers/zarr-python#3709

It's very likely that this gets fixed (meaning, consolidated metadata becomes spec-compliant) when the zarr governance updates (zarr-developers/zeps#69) come through, but worth noting in any case.