Canonicalize metro code description

Author: PatrickCroninMM

content/minfraud/minfraud-legacy.md

@@ -546,8 +546,8 @@ signed up for the service. The latest version is 1.3.
         <td>ip_metroCode</td>
         <td>integer</td>
         <td>
-          The metro code associated with the IP address. These are only
-          available for IP addresses in the US.
+          <strong>This field has been deprecated.</strong> This is a
+          no-longer-maintained code for targeting advertisements in Google.
         </td>
         <td>1.2</td>
       </tr>