Fix test code related to migrations

[tristan957]

We added another migration in 5876c44, but didn't bump this value. This had no effect, but best to fix it anyway.

[github-actions]

4994 tests run: 4830 passed, 0 failed, 164 skipped (full report)

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Flaky tests (7)

Postgres 17

• test_pageserver_compaction_smoke: release-arm64, release-x86-64
• test_tenant_import[4-real_s3]: release-x86-64
• test_scrubber_physical_gc[4]: release-arm64

Postgres 16

• test_slots_and_branching: release-x86-64
• test_scrubber_physical_gc[4]: release-arm64

Postgres 15

• test_ondemand_wal_download_in_replication_slot_funcs: release-arm64

Code coverage* (full report)

• functions: 32.0% (7413 of 23166 functions)
• lines: 49.9% (59577 of 119341 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
485f7b0 at 2024-09-17T03:40:04.699Z :recycle:}

[hlinnaka]

Is there a chance to refactor this somehow, so that we wouldn't need to remember to update this every time a new migration is added?

[tristan957]

Is there a chance to refactor this somehow, so that we wouldn't need to remember to update this every time a new migration is added?

Yes, let me give it some thought, and then I will ping you for a review.