update comments

Signed-off-by: Walther Lee <[email protected]>

config/config.go

@@ -41,7 +41,7 @@ var secretTokenJSON string
 
 // MarshalSecretValue if set to true will expose Secret type
 // through the marshal interfaces. Useful for outside projects
-// that load and marshal the Prometheus config.
+// that load and marshal the Alertmanager config.
 var MarshalSecretValue bool = commoncfg.MarshalSecretValue
 
 func init() {