Fix golint issue caused by typo
Fix golint issue caused by typo

Signed-off-by: Guangwen Feng <98e12d19818083ae8a98303786e6a151211377ea@cn.fujitsu.com>

GoogleCloudPlatform/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,keegancsmith/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,prometheus/prometheus,alileza/prometheus,alileza/prometheus,alileza/prometheus,prometheus/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus