Fix beats changelog docs

[Vinit023]

Removed append processor from 8.6.0 changelog entry and added it to 8.7.0 changelog

What does this PR do?

Why is it important?

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes [docs] Fix changelog entry for 8.6.0 #34340

Use cases

Screenshots

Move the 2nd bullet point from CHANGELOG.asciidoc to CHANGELOG.next.asciidoc

Logs

[botelastic]

This pull request doesn't have a Team:<team> label.

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @vinit-chauhan? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2023-01-30T17:15:34.964+0000

• Duration: 9 min 36 sec

❕ Flaky test report

No test was executed to be analysed.

🤖 GitHub comments

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To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

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[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b fix_changelog_entry_8.6 upstream/fix_changelog_entry_8.6
git merge upstream/main
git push upstream fix_changelog_entry_8.6

[leehinman]

LGTM