[w3c/webauthn] 0aef5b: Fix spec-build errors (editorial)

  Branch: refs/heads/jeffh-WD-03-fix-errors-prior-to-publishing
  Home:   https://github.com/w3c/webauthn
  Commit: 0aef5bf065e48042251d1c8bba78f0684ab5b0e3
      https://github.com/w3c/webauthn/commit/0aef5bf065e48042251d1c8bba78f0684ab5b0e3
  Author: JeffH <jdhodges@google.com>
  Date:   2020-07-29 (Wed, 29 Jul 2020)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Fix spec-build errors (editorial)

we have a few loose-end editorial link-errors and unreferenced dfns, this addresses almost all of those. there's one link-error remaining, am not sure yet how to deal with it.