Document that --serializer CLI argument is only available in 1.8.0

docs/docs/workers.md

@@ -69,6 +69,8 @@ In addition to `--burst`, `rq worker` also accepts these arguments:
 * `--date-format`: Datetime format for the worker logs, defaults to `'%H:%M:%S'`
 * `--disable-job-desc-logging`: Turn off job description logging.
 * `--max-jobs`: Maximum number of jobs to execute.
+
+_New in version 1.8.0._
 * `--serializer`: Path to serializer object (e.g "rq.serializers.DefaultSerializer" or "rq.serializers.JSONSerializer")
 
 ## Inside the worker
@@ -184,8 +186,6 @@ Aside from `worker.name`, worker also have the following properties:
 * `failed_job_count` - number of failed jobs processed
 * `total_working_time` - amount of time spent executing jobs, in seconds
 
-_New in version 0.10.0._
-
 If you only want to know the number of workers for monitoring purposes,
 `Worker.count()` is much more performant.
 
@@ -231,8 +231,6 @@ Queues will now use custom serializer
 
 ### Worker Statistics
 
-_New in version 0.9.0._
-
 If you want to check the utilization of your queues, `Worker` instances
 store a few useful information: