Clarify "SMS import complete" notification text

Fixes #5262
Closes #5274

// FREEBIE

res/values/strings.xml

@@ -595,7 +595,7 @@
     <string name="ApplicationMigrationService_import_in_progress">Import in progress</string>
     <string name="ApplicationMigrationService_importing_text_messages">Importing text messages</string>
     <string name="ApplicationMigrationService_import_complete">Import complete</string>
-    <string name="ApplicationMigrationService_Signal_system_database_import_is_complete">Signal system database import is complete.</string>
+    <string name="ApplicationMigrationService_system_database_import_is_complete">System database import is complete.</string>
 
     <!-- KeyCachingService -->
     <string name="KeyCachingService_signal_passphrase_cached">Touch to open.</string>

src/org/thoughtcrime/securesms/service/ApplicationMigrationService.java

@@ -189,7 +189,7 @@ public class ApplicationMigrationService extends Service
       NotificationCompat.Builder builder = new NotificationCompat.Builder(context);
       builder.setSmallIcon(R.drawable.icon_notification);
       builder.setContentTitle(context.getString(R.string.ApplicationMigrationService_import_complete));
-      builder.setContentText(context.getString(R.string.ApplicationMigrationService_Signal_system_database_import_is_complete));
+      builder.setContentText(context.getString(R.string.ApplicationMigrationService_system_database_import_is_complete));
       builder.setContentIntent(PendingIntent.getActivity(context, 0, new Intent(context, ConversationListActivity.class), 0));
       builder.setWhen(System.currentTimeMillis());
       builder.setDefaults(Notification.DEFAULT_VIBRATE);