Docs update - Group and project members API

• Documents Feature "Group and project members API"
• Follow-up from: #40202 (closed)

New doc or update?

• New documentation
• Update existing documentation

Checklists

Product Manager

• Add the correct labels
• Add the correct milestone
• Indicate the correct document/directory for this feature
• Fill the doc blurb below

Description

Changes are needed on this page: https://docs.gitlab.com/ce/api/members.html#list-all-members-of-a-group-or-project

Following up from #40202 (closed), we need to update the documentation to clarify the difference between api/projects/:id/members and api/projects/:id/members/all endpoints. Although #40202 (closed) is related to projects, we should also clarify this for api/groups/:id/members and api/groups/:id/members/all

Suggestions: For api/projects/:id/members, specify that it returns only the direct members. For api/projects/:id/members/all, specify that it returns inherited members and those added from another group.