Rename test to reference correct issue (encode#5610)

Author: Ryan P Kilby

tests/test_serializer.py

@@ -515,7 +515,7 @@ def test_validation_success(self):
         assert serializer.errors == {}
 
 
-class Test2505Regression:
+class Test2555Regression:
     def test_serializer_context(self):
         class NestedSerializer(serializers.Serializer):
             def __init__(self, *args, **kwargs):