Revert "Update to account for v16 changes"

What does this MR do and why?

This reverts merge request Update to account for v16 changes (!145483 - merged). That MR added incorrect information to the docs based on #356609 (comment 1136573847), without the additional context of #388988 (comment 1385129713):

Secure template changes for 16.0 (!119819 - merged) • rossfuhrman • 16.0 has been merged. It contains the majority of the changes. It DOES NOT contain any of the changes related to MR pipelines.

See also MR pipeline support in Sec templates (#410880).

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