Ensured lines don't exceed max length of 88

...to satisfy the Flake8 linter to allow the tests in #1130 to run.

Author: ddabble

simple_history/management/commands/clean_duplicate_history.py

@@ -39,9 +39,9 @@ def add_arguments(self, parser):
             "--base-manager",
             action="store_true",
             default=False,
-            help="Use Django's base manager to handle all records stored in the database,"
-            " including those that would otherwise be filtered or modified by a"
-            " custom manager.",
+            help="Use Django's base manager to handle all records stored in the"
+            " database, including those that would otherwise be filtered or modified"
+            " by a custom manager.",
         )
 
     def handle(self, *args, **options):