Downgrade No response from reading prefetch entry WARNING to LOG

[lubennikovaav]

Problem

This WARNING can be caused by normal reconnection, i.e. because of pageserver restart.
We don't need to keep it user-visible warning, because it is not actionable.

Summary of changes

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]

3192 tests run: 3054 passed, 0 failed, 138 skipped (full report)

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Flaky tests (2)

Postgres 15

• test_storage_controller_smoke: release

Postgres 14

• test_storage_controller_smoke: debug

Code coverage* (full report)

• functions: 31.5% (6605 of 20937 functions)
• lines: 48.5% (51074 of 105314 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
d45a9e6 at 2024-06-06T20:04:15.093Z :recycle:}