[#431] object/range: Fix payload slice allocation in re-sign callback

Allocate capacity instead of length of the slice to write the object payload
range since each chunk is written through `append`.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/object/get/v2/util.go

@@ -204,7 +204,7 @@ func (s *Service) toRangePrm(req *objectV2.GetRangeRequest, stream objectSvc.Get
 				return nil, errors.Wrap(err, "could not create Get payload range stream")
 			}
 
-			payload := make([]byte, body.GetRange().GetLength())
+			payload := make([]byte, 0, body.GetRange().GetLength())
 
 			resp := new(objectV2.GetRangeResponse)