Add missed parenthesis to make a method call for string

[Skyross]

That issue stopped me using DRF swagger and filter_backends together.

django-rest-framework/rest_framework/schemas/inspectors.py

Line 370 in 0f33e63

return method.lower in ["get", "put", "patch", "delete"]

[xordoquy]

Closing this as it is missing context.
There's a template that helps providing informations for bug reports so we can ensure it's not a user issue and someone can start working on it.

[carltongibson]

This was fixed in #5613.