fix autocluster example

[tureba]

The example had timestamptz as datatype and inserted only hour:minute unquoted.

Besides the obvious quoting, we should either change the data to match the datatype, or the datatype to match the hour:minute data. Using full timestamptz probably wouldn't improve the example, which is well served by simple data. So using time as column datatype is adequate.

This intends to cover issue #5486 .