code: public void deleteShardedLinkValue(String objID, FieldDefinition linkDef, String targetObjID, int shardNo) {
          assert linkDef.isSharded();
          assert shardNo > 0;
          deleteColumn(SpiderService.termsStoreName(linkDef.getTableDef()),
                       SpiderService.shardedLinkTermRowKey(linkDef, objID, shardNo),
                       targetObjID);
      }
docs: Delete a link value column in the Terms store for a sharded link.
  
  @param objID         ID of object that owns the link field.
  @param linkDef       {@link FieldDefinition} of (sharded) link field.
  @param targetObjID   ID of referenced object.
  @param shardNo       Shard number. Must be > 0.