❄️ Flaky test: amp-animation

Flaky test in `amp-animation`

```
1) amp-animation
chrome
AMPHTML ads FIE environment

transparency animation should pause and restart:

AssertionError: expected '0' to equal '1'
+ expected - actual

-0
+1

at valueSatisfiesExpectation (build-system/tasks/e2e/expect.js:376:18)
at conditionValue (build-system/tasks/e2e/selenium-webdriver-controller.js:121:22)
at _callee$ (build-system/tasks/e2e/selenium-webdriver-controller.js:86:46)
at tryCatch (build-system/tasks/e2e/node_modules/babel-regenerator-runtime/runtime.js:61:40)
at GeneratorFunctionPrototype.invoke [as _invoke] (build-system/tasks/e2e/node_modules/babel-regenerator-runtime/runtime.js:329:22)
at GeneratorFunctionPrototype.prototype. [as next] (build-system/tasks/e2e/node_modules/babel-regenerator-runtime/runtime.js:94:21)
at asyncGeneratorStep (build-system/tasks/e2e/selenium-webdriver-controller.js:11:103)
at _next (build-system/tasks/e2e/selenium-webdriver-controller.js:13:194)
at runMicrotasks ()
at processTicksAndRejections (internal/process/task_queues.js:93:5)
```

https://app.circleci.com/pipelines/github/ampproject/amphtml/5263/workflows/eebdd85b-86fc-448b-a3b9-3f33af6a0e6f/jobs/71532

@ampproject/wg-components

Start by reviewing the amp-animation end-to-end test named “transparency animation should pause and restart” and the failure context in build-system/tasks/e2e/expect.js and build-system/tasks/e2e/selenium-webdriver-controller.js. Use the linked CircleCI job to reproduce the failure, then verify that the test passes reliably in the AMPHTML ads FIE environment.

Written by the indexing model from the issue text.