Prune flaky examples after 30 days

What does this MR do?

Change the threshold after which we prune flaky examples from 90 to 30 days so that examples that are no longer flaky are pruned quicker than before.

We could even decrease this threshold further to have a quicker feedback loop after we fix flaky examples, but I think 30 days is a good first iteration.

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content