Add CSS Cascade 6, Scripting Policy, Close Watcher

This update adds CSS Cascade 6 and drops CSS Scoping 2 as a result (the latter
spec now redirects to the former).

It also adds the Scripting Policy and Close Watcher API. The two specs are
still at early stages but development is active and proposals are being backed
by implementers, see:
WICG/proposals#18
WICG/proposals#36

specs.json

@@ -11,6 +11,7 @@
   "https://drafts.css-houdini.org/font-metrics-api-1/",
   "https://drafts.csswg.org/css-animations-2/ delta",
   "https://drafts.csswg.org/css-backgrounds-4/ delta",
+  "https://drafts.csswg.org/css-cascade-6/ delta",
   "https://drafts.csswg.org/css-env-1/",
   "https://drafts.csswg.org/css-extensions-1/",
   "https://drafts.csswg.org/css-fonts-5/ delta",
@@ -26,7 +27,6 @@
     "shortTitle": "CSS Multicol 2"
   },
   "https://drafts.csswg.org/css-page-4/ delta",
-  "https://drafts.csswg.org/css-scoping-2/ delta",
   "https://drafts.csswg.org/css-shapes-2/ delta",
   {
     "url": "https://drafts.csswg.org/css-size-adjust-1/",
@@ -126,13 +126,15 @@
     "shortTitle": "Background Sync"
   },
   "https://wicg.github.io/client-hints-infrastructure/",
+  "https://wicg.github.io/close-watcher/",
   "https://wicg.github.io/compression/",
   "https://wicg.github.io/contact-api/spec/",
   "https://wicg.github.io/content-index/spec/",
   "https://wicg.github.io/conversion-measurement-api/",
   "https://wicg.github.io/cookie-store/",
   "https://wicg.github.io/crash-reporting/",
   "https://wicg.github.io/credentiallessness/",
+  "https://wicg.github.io/csp-next/scripting-policy.html",
   "https://wicg.github.io/css-parser-api/",
   "https://wicg.github.io/custom-state-pseudo-class/",
   "https://wicg.github.io/datacue/",