editorial: Reword requirements in "Security and privacy considerations"

[rakuco]

Use more modern spec terminology in the list of requirements for firing
device orientation and motion events:

• Use navigables and concepts defined for navigables when dealing with
  windows and documents.
• Stop referring to the PAGE-VISIBILITY spec, as it was merged into HTML a
  few years ago. Use a document's visibility state instead.
• Use more precise terms when laying out the same-origin requirements
  between the top-level traversable and its child navigables. The new
  paragraph is a mouthful, but also more precise.
• Instead of referring to the SECURE-CONTEXTS spec, use HTML's definition of
  "secure context".

This change should not cause any behavioral or user-detectable changes.

---

Preview | Diff