Add bug closure.

debian/changelog

@@ -2,7 +2,7 @@ dpkg (1.13.25~) UNRELEASED; urgency=low
 
   [ Guillem Jover ]
   * Fix year 2018 in changelog for Michael Alan Dorman's upload in 1998,
-    which was confusing the changelog parsers.
+    which was confusing the changelog parsers. Closes: #402526
   * Document in its man page that update-alternatives requires cooperation
     from all packages dealing with the specific file. Closes: #396338
     Thanks to Tomas Pospisek <tpo_deb@sourcepole.ch>.