adjust MDM migration copy and timers (#13366)

for #13158

changes/13158-nag-and-copy

@@ -0,0 +1 @@
+* Updated the copy and image displayed on the MDM migration modal

frontend/pages/admin/IntegrationsPage/cards/MdmSettings/components/EndUserMigrationSection/_styles.scss

@@ -7,6 +7,7 @@
 
   &__migration-preview {
     width: 100%;
+    max-width: 800px;
     margin-top: $pad-large;
     margin-bottom: $pad-xxlarge;
   }

orbit/pkg/useraction/mdm_migration_darwin.go

@@ -30,10 +30,9 @@ const (
 var mdmMigrationTemplate = template.Must(template.New("mdmMigrationTemplate").Parse(`
 ## Migrate to Fleet
 
-To begin, click "Start." Your default browser will open your My Device page.
-
-{{ if .IsUnmanaged }}You {{ else }} Once you start, you {{ end -}} will see this dialog every 15 minutes until you click "Turn on MDM" and complete the instructions.` +
-	"\n\n![Image showing the Fleet UI](https://fleetdm.com/images/permanent/mdm-migration-screenshot-768x180-2x.png)\n\n",
+Select **Start** and look for this notification in your notification center:` +
+	"\n\n![Image showing MDM migration notification](https://fleetdm.com/images/permanent/mdm-migration-notification-344x68.png)\n\n" +
+	"After you start, this window will popup every 5 minutes until you finish.",
 ))
 
 var errorTemplate = template.Must(template.New("").Parse(`