xref for "xr-standard" gamepad mapping not working

[nondebug]

Description of problem

This PR is blocked on this issue:
w3c/gamepad#168

What happened (e.g., it crashed)?:

Error: ROR] Couldn’t find “"xr-standard" gamepad mapping“ in this document or other cited documents: [dom], [hr-time], [html], [infra], [permissions-policy], [webidl], and [webxr-gamepads-module].

Expected behavior (e.g., it shouldn't crash):

Working xref

Optional, steps to reproduce:

1. ...

[sidvishnoi]

With some bisecting, I was able to find this regress in https://github.com/w3c/respec/pull/4439 https://github.com/w3c/respec/pull/4431. Now onto debugging...