Update VSA in left nav

Update navigation items in global navigation

The pages "Value Stream Analytics for groups" and "Value Stream Analytics for projects" were consolidated into "Value Stream Analytics". This MR removes the extra navigation item and renames the remaining one.

• Link to the merge request that introduced the new page: gitlab!115882 (merged)
• Give the MR a descriptive title.
• Optional. Link to the review app showing the new page: https://lc-update-vsa-nav.docs.gitlab-review.app/ee/user/group/value_stream_analytics/