Remove smartmon run metric

This metric is a bit funny, it's a timestamp per device, but it's not
accurate enough (seconds, not milliseconds) to derive much useful
information from it. This should probably be replaced with a per-device
duration metric.

Signed-off-by: SuperQ <superq@gmail.com>

smartmon.py

@@ -326,11 +326,7 @@ def collect_ata_error_count(device):
 
 
 def collect_disks_smart_metrics(wakeup_disks):
-    now = int(datetime.datetime.utcnow().timestamp())
-
     for device in find_devices():
-        yield Metric('smartctl_run', device.base_labels, now)
-
         is_active = device_is_active(device)
 
         yield Metric('device_active', device.base_labels, is_active)