Remove or modify defined term "Security Support System"

[clintwilson]

Based on current usage of the defined term "Security Support System", it seems that the NCSSRs may benefit more from focusing on describing the outcomes of a CA using Security Support Systems rather than defining what a Security Support System is. These outcomes should be explicit within the requirements themselves regardless, and if they are, it's plausible that the necessity of a related defined term is diminished or removed.