Deprecate --min-block-occupancy-ratio for removal and make it noop

[fab-10]

PR description

Deprecate --min-block-occupancy-ratio for removal and make it noop. That option, that is ignored on PoS networks, is related to the deprecated PoW, and allowed to broadcast a mined block as soon as it reached a satisfying fill threshold. The option is still recognized, but it has no effect and will be completely removed in a future release.

Fixed Issue(s)

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• Checked out our contribution guidelines?
• Considered documentation and added the doc-change-required label to this PR if updates are required.
• Considered the changelog and included an update if required.
• For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• spotless: ./gradlew spotlessApply
• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests
• hive tests: Engine or other RPCs modified?

[fab-10]

@matthew1001 to double check, do you see any issue with this PR?

[fab-10]

@macfarla do you think this should wait full PoW removal?