Increase time after FF switching

What does this MR do and why?

Describe in detail what your merge request does and why.

Observing from failure that after running example with FF enabled successfully, the example disabled the flag and sleep 30. But that wasn't enough sometimes, thus resulted in the following example running with flag disabled was still acting as if flag was enabled and failed.

With the failed job passed at retry and flag is temporary, increase sleeping time to reduce failure noises.

Related to known issue #36663

MR acceptance checklist

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Related to #384523 (closed)