Bug 1591592 [wpt PR 19902] - Update wpt metadata, a=testonly

wpt-pr: 19902
wpt-type: metadata

Differential Revision: https://phabricator.services.mozilla.com/D53487

testing/web-platform/meta/css/css-ui/outline-018.html.ini

@@ -1,4 +0,0 @@
-[outline-018.html]
-  [outline-style is animated as a discrete type]
-    expected: FAIL
-