Change docs metadata on projects-related pages to Manage: Workspace

What does this MR do and why?

As per #340506 (closed), this MR changes docs metadata on projects-related pages to Manage: Workspace.

Pages confirmed for update:

• https://gitlab.com/gitlab-org/gitlab/blob/master/doc/user/project/index.md
• https://gitlab.com/gitlab-org/gitlab/blob/master/doc/user/project/working_with_projects.md
• https://gitlab.com/gitlab-org/gitlab/blob/master/doc/user/project/settings/index.md
• https://gitlab.com/gitlab-org/gitlab/blob/master/doc/public_access/public_access.md
• https://gitlab.com/gitlab-org/gitlab/blob/master/doc/user/project/members/share_project_with_groups.md
• https://gitlab.com/gitlab-org/gitlab/blob/master/doc/user/reserved_names.md

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

Related to #340506 (closed)