code: func dropDisabledProcMountField(podSpec, oldPodSpec *api.PodSpec) {
  	if !utilfeature.DefaultFeatureGate.Enabled(features.ProcMountType) && !procMountInUse(oldPodSpec) {
  		defaultProcMount := api.DefaultProcMount
  		for i := range podSpec.Containers {
  			if podSpec.Containers[i].SecurityContext != nil {
  				podSpec.Containers[i].SecurityContext.ProcMount = &defaultProcMount
  			}
  		}
  		for i := range podSpec.InitContainers {
  			if podSpec.InitContainers[i].SecurityContext != nil {
  				podSpec.InitContainers[i].SecurityContext.ProcMount = &defaultProcMount
  			}
  		}
  	}
  }
docs: // dropDisabledProcMountField removes disabled fields from PodSpec related
  // to ProcMount only if it is not already used by the old spec