Set debhelper-compat version in Build-Depends.

Changes-By: lintian-brush
Fixes: lintian: uses-debhelper-compat-file
See-also: https://lintian.debian.org/tags/uses-debhelper-compat-file.html

debian/compat

-13

debian/control

@@ -2,7 +2,7 @@ Source: gitlab-deps
 Section: net
 Priority: extra
 Maintainer: Autistici/Inventati <debian@autistici.org>
-Build-Depends: debhelper (>= 13~), dh-python, python3,
+Build-Depends: debhelper-compat (= 13), dh-python, python3,
 Standards-Version: 4.1.3
 
 Package: gitlab-deps