Move SAML Group Sync navigation item

As discussed in: gitlab!91549 (closed), Group Sync is no longer SaaS only, so looks out of place under: http://127.0.0.1:3000/ee/user/group/saml_sso/. This MR moves it to be next to that navigation item instead.

• Before: https://docs.gitlab.com/ee/user/group/saml_sso/group_sync.html
• After: http://eread-move-saml-group-sync-navigation-item.35.193.151.162.nip.io/ee/user/group/saml_sso/group_sync.html