Remove jakarta.faces.visit.SKIP_ITERATION

[BalusC]

Discovered while looking at jakartaee/faces#1853

RestoreViewPhase has this since JSF 2.0:

// PENDING: This is included for those component frameworks that don't utilize the
// new VisitHint(s) yet - but still wish to know that they should be non-iterating
// during state saving. It should be removed at some point.
facesContext.getAttributes().put(SKIP_ITERATION_HINT, true);

It has been superseded by https://jakarta.ee/specifications/platform/10/apidocs/jakarta/faces/component/visit/visithint. It's time to remove it. It can be done safely, it's nowhere documented in spec.

Its original value is javax.faces.visit.SKIP_ITERATION and it has since 3.0 even been renamed to jakarta.faces.visit.SKIP_ITERATION without being removed.