remove .Sx attempt at cross-linking in mac manuals
When doing work on the mac manuals, we often tried to cross-reference to a specific section of another manual. We've sometimes referred to the name of the other section with
.Sx which is meant to be a link to a sub-section, but only in the current document. Until a macro for cross-linking to a specific section of another document exists, we should just normalize these to using
.Sy like we do in librpoc and others.