Decorate `test_codegen_sample_max_time` as flaky
# What does this PR do?

Decorate `test_codegen_sample_max_time` as flaky: it fails 0-5 times per month.
_The documentation is not available anymore as the PR was closed or merged._<|||||>I agree! Probably we can use something like `@cached_property`: I see this but never use it myself so far.<|||||>OK. But can I keep `cache_proeprty` as in the current version (it at least avoids loading the checkpoint despite it is downloaded).
I see there are few modeling test files doing this.<|||||>If you really want to!