Remove unenforced traversal directive option

What does this MR do and why?

The traversal argument on the GranularScope GraphQL directive was declared but never enforced — fields marked traversal: true checked their listed permissions like any other field. This MR removes the unused argument, the granular_scope_directive(traversal:) and authorize_granular_token(traversal:) keywords, the type-level ArgumentError validation, and related documentation sections. Introspection artifacts are regenerated. No behavior changes.

Part 1 of 3 splitting up !242976 (closed). Selection-based traversal replaces the concept in part 2.

References

• !242976 (closed) (original MR)