Simplify index destruction

We do not have to create indexes right now, it's enought to cleanup the
storage.
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/search.py

@@ -60,9 +60,7 @@ def clean_indexes():
     """
     Cleans all indexes.
     """
-    create_source_index()
-    for lang in Language.objects.have_translation():
-        create_target_index(lang=lang.code)
+    STORAGE.clean()
 
 
 @receiver(post_migrate)