erp5: Re-add release-critical issue about parameters.

As test database count could not yet be changed to 0, this point is still
a blocker.

stack/erp5/TODO

+Release critical:
+- default number of test relation databases must be 0
+  This requires erp5 test nodes to be updated to a version where the correct number of databases is requested
+
 General:
 - varnish/squid
 - ipv6 support (besides frontend-backend apache connection)