core: repair ERP5Site_reindexLatestIndexedObjects

This script stopped working since Catalog changed to be ERP5 document,
because it was calling the unindex method of the catalog (which
itself is indexable like any other ERP5 document). Update to use the
uncatalogObject which is the method to unindex a document by uid.

Even though it was somehow working before, it was not really correct
in selecting objects, because it was using - operator on TIMESTAMP
column, which is not computing a difference in seconds as this script
was expecting. See for example https://stackoverflow.com/a/24504132/7607763
or the example below for an explanation. Instead, use TIMESTAMPADD
to compute the start timestamp only once and use >= operator, which
works as expected.

This query was also sorting by indexation_timestamp, which does not
use an index. Remove the sort because it's not really needed.

Excluding reserved path was also not needed, we no longer use these
since 69aefdff (ZSQLCatalog: Drop support for "reserved" path.,
2017-09-18)

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Another reproduction of the timestamp arithmetic problem

select
   TIMESTAMP('2021-01-02 00:00:00') - TIMESTAMP('2021-01-01 00:00:00') a,
   20210102000000 - 20210101000000 aa,
   TIMESTAMP('2021-06-01 00:00:00') - TIMESTAMP('2021-05-31 00:00:00') b,
   20210601000000 - 20210531000000 bb,
   TIMESTAMPDIFF(second, TIMESTAMP('2021-05-31 00:00:00'), TIMESTAMP('2021-06-01 00:00:00')) c

| a | aa | b | bb | c |
| ------ | ------ | ------ | ------ | ------ |
| 1000000 | 1000000 | 70000000 | 70000000 | 86400 |