Remove unmapped media galleries histograms.

components/storage_monitor/storage_monitor_mac.mm

Index: components/storage_monitor/storage_monitor_mac.mm
diff --git a/components/storage_monitor/storage_monitor_mac.mm b/components/storage_monitor/storage_monitor_mac.mm
index 47d91355febafeedafb8fa4e8197980dc6d80f20..a48b02493f33742b4f8198669d9f020b9fbd3047 100644
--- a/components/storage_monitor/storage_monitor_mac.mm
+++ b/components/storage_monitor/storage_monitor_mac.mm
@@ -238,8 +238,6 @@ void StorageMonitorMac::UpdateDisk(
       disk_info_map_.erase(it);
   } else {
     disk_info_map_[bsd_name] = info;
-    MediaStorageUtil::RecordDeviceInfoHistogram(true, info.device_id(),
-                                                info.storage_label());
     if (ShouldPostNotificationForDisk(info))
       receiver()->ProcessAttach(info);
   }