Update standards version to 4.1.5, no changes needed.

Changes-By: lintian-brush
Fixes: lintian: ancient-standards-version
See-also: https://lintian.debian.org/tags/ancient-standards-version.html

debian/control

@@ -5,7 +5,7 @@ Maintainer: Mailman for Debian <pkg-mailman-hackers@lists.alioth.debian.org>
 Uploaders: Thijs Kinkhorst <thijs@debian.org>,
 Build-Depends: debhelper-compat (= 13), autoconf, python-dev,
  gettext, python-dnspython, dh-python
-Standards-Version: 4.1.4
+Standards-Version: 4.1.5
 Homepage: https://www.list.org/
 Vcs-Git: https://salsa.debian.org/mailman-team/mailman2.git
 Vcs-Browser: https://salsa.debian.org/mailman-team/mailman2