Fixed DatabaseFeatures.requires_literal_defaults on SQLite.

This flag is currently unused on SQLite because it doesn't support
dropping a DEFAULT clause, however it requires literal defaults, rather
than parameterized ones, so we can set it for clarity.

django/db/backends/sqlite3/features.py

@@ -18,6 +18,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     can_rollback_ddl = True
     can_create_inline_fk = False
     supports_paramstyle_pyformat = False
+    requires_literal_defaults = True
     can_clone_databases = True
     supports_temporal_subtraction = True
     ignores_table_name_case = True