Use small sample document for checkout app tests.

mayan/apps/checkouts/tests/test_models.py

@@ -35,7 +35,7 @@ class DocumentCheckoutTestCase(TestCase):
             label=TEST_DOCUMENT_TYPE
         )
 
-        with open(TEST_DOCUMENT_PATH) as file_object:
+        with open(TEST_SMALL_DOCUMENT_PATH) as file_object:
             self.document = self.document_type.new_document(
                 file_object=File(file_object)
             )