release-23.2: roachtest: bump timeout of failover/chaos tests

[blathers-crl]

Backport 1/1 commits from #124035 on behalf of @nvanbenschoten.

/cc @cockroachdb/release

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Fixes #124030.

The test runs 20 iterations of failures, each of which include 3 sleeps, two of which take 1 minute. This is not quite enough time so the test occasionally times out when it is otherwise making progress.

Release note: None

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Release justification: test only.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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[cockroach-teamcity]

This change is