Update spec URL for gamepad permission policy (#11954)
Update spec URL for gamepad permission policy (#11954)

* In general, should link to w3c.github.io spec versions rather than
  www.w3.org/TR — because many of the www.w3.org/TR are out of date,
  while the w3c.github.io versions always reflect the latest changes.

* In general, should link to the closest heading ID, when it makes
  sense, not necessarily to the most-specific dfn ID — because linking
  to the heading immediately orients the reader/developer, with more
  context,  in a way that linking deeper in doesn’t.

  For example, a developer following a link to the specific anchor
  https://w3c.github.io/gamepad/#dfn-gamepad won’t even see the
  “Integration with Permissions Policy” heading, because they get
  scrolled past it. But a developer following a link to
  https://w3c.github.io/gamepad/#permission-policy will immediately see
  the heading and the entire content of the section — so it provides
  more context and clarity for them as a reader.
chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data