Bug 1675141 [wpt PR 26366] - Update wpt metadata, a=testonly

wpt-pr: 26366
wpt-type: metadata

testing/web-platform/meta/css/css-transforms/animation/transform-interpolation-rotate-slerp.html.ini

@@ -0,0 +1,2 @@
+[transform-interpolation-rotate-slerp.html]
+  expected: FAIL

testing/web-platform/meta/css/css-transforms/animation/transform-interpolation-rotate.html.ini

@@ -1,2 +1,4 @@
 [transform-interpolation-rotate.html]
-  expected: FAIL
+  expected:
+    if webrender: PASS
+    FAIL