[CHANGELOG] remove docs updates from changelog

[macfarla]

PR description

Besu docs used to be part of besu repo.
This is why documentation updates are listed in the besu changelog for older versions of besu
This PR removes those entries from the changelog - no longer relevant and also containing links that are likely to be or become out of date.

Fixed Issue(s)

Thanks for sending a pull request! Have you done the following?

• 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:

• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests

[macfarla]

Think this is a better option than keeping links up to date as per #7558

We could go further and delete anything that's already been released - discussion in discord https://discord.gg/hyperledger

[fab-10]

LGTM, probably worth adding a changelog entry describing the change