Update deprecated configuration settings documentation

[belkhoujaons]

Summary

Remove deprecated configuration setting from product documentation

Ticket Link

Fixes #7460

[mattermost-build]

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[github-actions]

Newest code from belkhoujaons has been published to preview environment for Git SHA 0c6f524

[cwarnermm]

Thanks, @belkhoujaons!!

Please also remove the following text from that page:

Mattermost Boards setting
--------------------------

*Removed in the Mattermost v8.0 release*

[belkhoujaons]

Thanks, @belkhoujaons!!

Please also remove the following text from that page:

Mattermost Boards setting
--------------------------

*Removed in the Mattermost v8.0 release*

done !

[cwarnermm]

@belkhoujaons - Are you open to signing the Mattermost CLA? This step is required in order to merge your changes into the documentation code base.

[cwarnermm]

Thank you, @belkhoujaons!!

[belkhoujaons]

@belkhoujaons - Are you open to signing the Mattermost CLA? This step is required in order to merge your changes into the documentation code base.

I just signed for that and it needs approval

[cwarnermm]

@belkhoujaons - Please comment in this PR with /check-cla and confirm that the CLA check is green. If it isn't, I'll investigate further.

[belkhoujaons]

/check-cla

[Rutam21]

@lindy65 You can assign this to me for QA Testing. Thanks.

[Rutam21]

@cwarnermm Please generate another preview environment so that it includes the latest commits in the PR. Thanks.

[lindy65]

Assigned to you @Rutam21 and kicked off a new preview environment

[github-actions]

Newest code from belkhoujaons has been published to preview environment for Git SHA a30db42

[github-actions]

Newest code from belkhoujaons has been published to preview environment for Git SHA 54eba32

[Rutam21]

The changes in this PR have been tested in the preview environment and all the required updates are available in the mentioned pages.

• The Mattermost Board Settings section doesn't show up on the Deprecated Configuration Settings page on the Docs Site.
• The Mattermost Board Settings link doesn't show up on the top of this page and is removed from the table of contents.
• Searching for the Mattermost Board Settings or Enable publicly-shared boards doesn't return a result in the Additional Information section that points to this removed section.

I've attached a video as a confirmation.

PR-7461.QA.Testing.mp4

cc: @lindy65

[lindy65]

Thanks for testing @Rutam21 - counted towards Hacktoberfest!

cc @cwarnermm