Increase timeout for wating subscriner 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.

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.
• [ ] Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• [ ] 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[bot]]

3228 tests run: 3111 passed, 0 failed, 117 skipped (full report)

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Flaky tests (2)

#### Postgres 15 - `test_subscriber_restart`: [debug](https://neon-github-public-dev.s3.amazonaws.com/reports/pr-8118/9593865194/index.html#suites/8be0c222d5601535470e7e5978bbfb03/e5bda8926b448499/retries) #### Postgres 14 - `test_subscriber_restart`: [debug](https://neon-github-public-dev.s3.amazonaws.com/reports/pr-8118/9593865194/index.html#suites/8be0c222d5601535470e7e5978bbfb03/eacec62eea607a8f/retries)

Code coverage* (full report)

• functions: 32.3% (6846 of 21165 functions)
• lines: 49.7% (53395 of 107360 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
d0b82bdf1b9d596480e63a0c6e41224b64f46ce3 at 2024-06-20T08:56:39.734Z :recycle:}