Remove inert check from dialog focusing steps

[nt1m]

The focus fixup rule should reset focus to body in the modal case, and no element will be focused in the non-modal case. So the behavior stays the same after and before this PR in terms of focused element

• At least two implementers are interested (and none opposed):
  • Webkit
  • Chromium: https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/html/html_dialog_element.cc;l=48;drc=f4b6354a57a403a0b56b940104013cda4c37a7af
  • Gecko: https://searchfox.org/mozilla-central/rev/553bf8428885dbd1eab9b63f71ef647f799372c2/dom/html/HTMLDialogElement.cpp#149
• Tests are written and can be reviewed and commented upon at:
  • Expand and change dialog focus delegation tests web-platform-tests/wpt#31724
• Implementation bugs are filed:
  • Chrome: N/A
  • Firefox: N/A
  • Safari: TODO

(See WHATWG Working Mode: Changes for more details.)

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/acknowledgements.html ( diff )
/interactive-elements.html ( diff )