Old variable name in navigation test

[mattgarrish]

In the epub techniques, the navigation section has this test in 4.5.3:

IF table_of_contents_navigation OR index_navigation OR print_equivalent_page_numbering OR next_previous_structural_navigation:

but it appears that print_equivalent_page_numbering was changed to page_navigation.

[mattgarrish]

The old variable is back in the document again. I think this might be related to the comment I made in #570 (comment) about the complementary audio and text output still being there.

We might need to check some of the old pull request merges and see if one of them accidentally undid recent changes. I'll keep reporting what I notice, though.

[mattgarrish]

It appears the change back was made here: https://github.com/w3c/publ-a11y/pull/557/files#diff-41b03dc592ecd0fab9885a994d30555c093d6a362ef762f8234c1fe4b373b4c5L641

The onix techniques uses "print_equivalent_page_numbering" so maybe we should pick on one or the other and use it in both documents?