safekeeper: remove unused partial_backup_enabled option

[dotdister]

Problem

There is an unused safekeeper option partial_backup_enabled.

partial_backup_enabled was implemented in #6530, but this option was always turned into enabled in #8022.

If you intended to keep this option for a specific reason, I will close this PR.

Summary of changes

I removed an unused safekeeper option partial_backup_enabled.

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

[arpad-m]

Thanks for the PR @dotdister ! It seems that we still set the flag in our internal deployments, even though as you correctly point out it is redundant. I have initiated the process of removing it from our deployments (internal link https://github.com/neondatabase/aws/pull/1660 ).

[github-actions]

3138 tests run: 3017 passed, 0 failed, 121 skipped (full report)

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Code coverage* (full report)

• functions: 32.8% (7024 of 21387 functions)
• lines: 50.0% (55895 of 111712 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
36e49ab at 2024-07-30T12:16:07.145Z :recycle:}

[arpad-m]

The internal changes were applied and will be rolled out at the next week's deploy. To make sure the option is really gone from config files, I think we should merge this next week.

[dotdister]

Thank you for quick review and response for internal use !

The internal changes were applied and will be rolled out at the next week's deploy. To make sure the option is really gone from config files, I think we should merge this next week.

Yes, I understand. I will wait for the next week's deploy.