google-cloud-trace `ITSystemTest#getTraceTest()` is flaky

> This one was quite flaky when trying the integration test. The timeout seemed to help.

_Originally posted by @diegomarquezp in [#12730](https://github.com/googleapis/google-cloud-java/pull/12730/changes#r3156926610)_

While this approach sorts out the problem, we will temporarily disable this test with `@Ignore` while we find a better solution.