tests(smoke): fix failureReasonsMask flake (#11791)

lighthouse-cli/test/smokehouse/test-definitions/perf/expectations.js

@@ -240,7 +240,10 @@ module.exports = [
           animations: [
             {
               name: 'anim',
-              failureReasonsMask: 8224,
+              // The animation reliably gets kUnsupportedCSSProperty (1 << 13) === 8192.
+              // Sometimes it also gets kTargetHasInvalidCompositingState (1 << 5) == 32. Together they sum to 8224.
+              // Both are fine for our purposes.
+              failureReasonsMask: '8192 +/- 32',
               unsupportedProperties: ['background-color'],
             },
           ],