Add support for SCCS v6

[anthonysena]

SCCS v6 will be released soon and Strategus has modifications to the analysis specification to support it here: https://github.com/OHDSI/Strategus/blob/fe73766233df1d2b58334a5edc9d8b4c045b50b7/R/Module-SelfControlledCaseSeries.R#L49

[jreps]

fixed in recent release