[scroll-animations-1] Update status to ED

Per CSSWG resolution [1], we graduated this specification from WICG to CSSWG
a while back. So this is an official ED spec for CSSWG. The status and level
are updated to reflect this.

[1] w3c#4337 (comment)

Author: majido

scroll-animations-1/Overview.bs

@@ -2,8 +2,9 @@
 <pre class='metadata'>
 Title: Scroll-linked Animations
 Group: CSSWG
-Status: UD
+Status: ED
 Work Status: exploring
+Level: 1
 Group: CSSWG
 URL: https://drafts.csswg.org/scroll-animations-1/
 ED: https://drafts.csswg.org/scroll-animations-1/