debian/rules: try again to disable tests

- seems you need to leave the target override in place, but empty, or it
  does something all by itself

debian/rules

@@ -4,3 +4,7 @@ export PYBUILD_NAME := ligo-segments
 
 %:
 	dh $@ --with python2,python3 --buildsystem=pybuild
+
+# do not run tests at all.
+override_dh_auto_test:
+	true