docs: remove references to the deleted rangetree
docs: remove references to the deleted rangetree

Part of #9634.

vaibhavarora/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,glycerine/cockroach,cockroachdb/cockroach,maxlang/cockroach,maxlang/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,maxlang/cockroach,maxlang/cockroach,glycerine/cockroach,paperstreet/cockroach,petermattis/cockroach,petermattis/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,paperstreet/cockroach,cockroachdb/cockroach,paperstreet/cockroach,paperstreet/cockroach,glycerine/cockroach,glycerine/cockroach,petermattis/cockroach,glycerine/cockroach,vaibhavarora/cockroach,glycerine/cockroach,paperstreet/cockroach,maxlang/cockroach,maxlang/cockroach,petermattis/cockroach,petermattis/cockroach,veteranlu/cockroach,cockroachdb/cockroach,petermattis/cockroach,maxlang/cockroach,cockroachdb/cockroach,veteranlu/cockroach,veteranlu/cockroach,cockroachdb/cockroach,paperstreet/cockroach,glycerine/cockroach,veteranlu/cockroach,petermattis/cockroach,veteranlu/cockroach,veteranlu/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,glycerine/cockroach,veteranlu/cockroach,maxlang/cockroach,petermattis/cockroach,veteranlu/cockroach,vaibhavarora/cockroach