Bug 1966587 [wpt PR 52564] - Update wpt metadata,

wpt-pr: 52564
wpt-type: metadata

Differential Revision: https://phabricator.services.mozilla.com/D250620

UltraBlame original commit: da86dd513fa3275cb4eedcdbbc6f4eb5a70b94e9

Author: marco-c

testing/web-platform/meta/css/css-values/tree-counting/sibling-index-keyframe-rotate-dynamic.html.ini

@@ -0,0 +1,6 @@
+[sibling-index-keyframe-rotate-dynamic.html]
+  [Initially, the sibling-index() is 3 for #target]
+    expected: FAIL
+
+  [Removing a preceding sibling of #target reduces the sibling-index()]
+    expected: FAIL