Fix an error in 'application_metrics.md'
Fix an error in 'application_metrics.md'

There is a minor mistake of Dockerfile example
erSitzt/cadvisor,derekwaynecarr/cadvisor,linux-on-ibm-z/cadvisor,derekwaynecarr/cadvisor,erSitzt/cadvisor,erSitzt/cadvisor,derekwaynecarr/cadvisor,linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor,derekwaynecarr/cadvisor,erSitzt/cadvisor,erSitzt/cadvisor,derekwaynecarr/cadvisor