Fix argument help for Workhorse apiCiLongPollingDuration command

Previously `gitlab-workhorse --help` would show:

```
Long polling duration for job requesting for runners (default 50s -
enabled) (default 50ns)
```

Now it shows:

```
Long polling duration for job requesting for runners (default 50ns)
```

workhorse/doc/operations/configuration.md

@@ -11,7 +11,7 @@ All new configuration options that get added to Workhorse should go into the con
 
 Options:
   -apiCiLongPollingDuration duration
-      Long polling duration for job requesting for runners (default 50s - enabled) (default 50ns)
+      Long polling duration for job requesting for runners (default 50ns)
   -apiLimit uint
       Number of API requests allowed at single time
   -apiQueueDuration duration

workhorse/main.go

@@ -102,7 +102,7 @@ func buildConfig(arg0 string, args []string) (*bootConfig, *config.Config, error
 	fset.UintVar(&cfg.APILimit, "apiLimit", 0, "Number of API requests allowed at single time")
 	fset.UintVar(&cfg.APIQueueLimit, "apiQueueLimit", 0, "Number of API requests allowed to be queued")
 	fset.DurationVar(&cfg.APIQueueTimeout, "apiQueueDuration", queueing.DefaultTimeout, "Maximum queueing duration of requests")
-	fset.DurationVar(&cfg.APICILongPollingDuration, "apiCiLongPollingDuration", 50, "Long polling duration for job requesting for runners (default 50s - enabled)")
+	fset.DurationVar(&cfg.APICILongPollingDuration, "apiCiLongPollingDuration", 50, "Long polling duration for job requesting for runners")
 	fset.BoolVar(&cfg.PropagateCorrelationID, "propagateCorrelationID", false, "Reuse existing Correlation-ID from the incoming request header `X-Request-ID` if present")
 
 	if err := fset.Parse(args); err != nil {