Fix pushGateway options

[autowp]

Ref:

Usage of pagespeed_exporter:
  -api-key string
    	sets the google API key used for pagespeed
  -listener string
    	sets the listener address for the exporters (default ":9271")
  -parallel
    	forces parallel execution for pagespeed
  -pushGatewayJob string
    	sets push gateway job name (default "pagespeed_exporter")
  -pushGatewayUrl string
    	sets the push gateway to send the metrics. leave empty to ignore it
  -t value
    	multiple argument parameters
  -targets string
    	comma separated list of targets to measure