cli: update the external dependency on readline.
cli: update the external dependency on readline.

This fixes an error when loading a previously saved command history
containing empty lines.

maxlang/cockroach,cockroachdb/cockroach,paperstreet/cockroach,maxlang/cockroach,cockroachdb/cockroach,petermattis/cockroach,maxlang/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,paperstreet/cockroach,paperstreet/cockroach,sunya123/cockroach,paperstreet/cockroach,petermattis/cockroach,arjun4084346/cockroach,veteranlu/cockroach,maxlang/cockroach,petermattis/cockroach,vivekmenezes/cockroach,maxlang/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,glycerine/cockroach,glycerine/cockroach,vaibhavarora/cockroach,arjun4084346/cockroach,paperstreet/cockroach,veteranlu/cockroach,paperstreet/cockroach,sunya123/cockroach,arjun4084346/cockroach,sunya123/cockroach,sunya123/cockroach,glycerine/cockroach,vivekmenezes/cockroach,vivekmenezes/cockroach,arjun4084346/cockroach,petermattis/cockroach,sunya123/cockroach,arjun4084346/cockroach,petermattis/cockroach,glycerine/cockroach,veteranlu/cockroach,glycerine/cockroach,petermattis/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,sunya123/cockroach,sunya123/cockroach,cockroachdb/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,petermattis/cockroach,glycerine/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,arjun4084346/cockroach,maxlang/cockroach,glycerine/cockroach,paperstreet/cockroach,cockroachdb/cockroach,paperstreet/cockroach,arjun4084346/cockroach,maxlang/cockroach,veteranlu/cockroach,petermattis/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,maxlang/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,sunya123/cockroach,glycerine/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach