Increase timeout for wating subscriber caught-up

[knizhnik]

Problem

test_subscriber_restart has quit large failure rate'
https://neonprod.grafana.net/d/fddp4rvg7k2dcf/regression-test-failures?orgId=1&var-test_name=test_subscriber_restart&var-max_count=100&var-restrict=false

I can be caused by too small timeout (5 seconds) to wait until changes are propagated.

Related to #8097

Summary of changes

Increase timeout to 30 seconds.

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
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• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

3024 tests run: 2909 passed, 0 failed, 115 skipped (full report)

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Flaky tests (2)

Postgres 16

• test_multixid_wraparound_import: debug

Postgres 14

• test_subscriber_restart: release

Code coverage* (full report)

• functions: 32.6% (6934 of 21275 functions)
• lines: 50.0% (54490 of 108968 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
eac010c at 2024-07-05T14:50:32.106Z :recycle:}

[ololobus]

Jumping from 10 right to 60 maybe a bit too much. I'd maybe consider 40 as an intermediate step, but otherwise let's try. If it won't help, there could be a moer fundamental issue