Update watch file format version to 4.

Changes-By: lintian-brush
Fixes: lintian: older-debian-watch-file-standard
See-also: https://lintian.debian.org/tags/older-debian-watch-file-standard.html

debian/changelog

+python-validictory (1.1.2-2) UNRELEASED; urgency=medium
+
+  * Update watch file format version to 4.
+
+ -- Debian Janitor <janitor@jelmer.uk>  Wed, 15 Sep 2021 00:39:24 -0000
+
 python-validictory (1.1.2-1) unstable; urgency=medium
 
   [ Ondřej Nový ]

debian/watch

-version=3
+version=4
 https://github.com/sunlightlabs/validictory/tags .*/(.*)\.tar\.gz