tsdb/chunks: remove un-used code. (#6944)
tsdb/chunks: remove un-used code. (#6944)

Signed-off-by: johncming <64aa7c399bffb85fffaccf95be9acb9553c38de5@yahoo.com>
keegancsmith/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,alileza/prometheus,keegancsmith/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,prometheus/prometheus,prometheus/prometheus,alileza/prometheus