[css-mediaqueries-4] Remove "at-risk" for the '@media/update' media feature (#8571)

Author: danielsakhapov

mediaqueries-4/Overview.bs

@@ -32,7 +32,6 @@ Ignore Can I Use URL Failure: http://drafts.csswg.org/mediaqueries-4/
 Ignore Can I Use URL Failure: https://drafts.csswg.org/mediaqueries/
 Ignore Can I Use URL Failure: http://drafts.csswg.org/mediaqueries/
 Ignore Can I Use URL Failure: http://www.w3.org/TR/mediaqueries-4/
-At Risk: The '@media/update' media feature
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