Revert "IBX-9452: Describe segment and segment group REST endpoints (#2624)"

This reverts commit 567bef7.

Author: dabrt

docs/api/rest_api/rest_api_reference/input/examples/segment_groups/POST/SegmentGroup.json.example

@@ -4,4 +4,4 @@
         "_href": "\/api\/ibexa\/v2\/segment_groups\/corporate_accounts\/segments",
         "Segment": []
     }
-}
+}