Simplify ignore rules

Signed-off-by: Michal Čihař <michal@cihar.com>

.landscape.yaml

@@ -5,6 +5,5 @@ uses:
 autodetect: yes
 ignore-paths:
   - docs
+  - south_migrations
   - weblate/trans/tests/__init__.py
-ignore-patterns:
-  - ^weblate/[^/]*/south_migrations