feat: ignore basic auth header if empty

[reubenmiller]

Update go-c8y library to include a fix where the Authorization header should be ignored if the username or password is empty.

This enables usage with thin-edge.io by just specifying one environment variable C8Y_HOST:

C8Y_HOST=http://localhost:8001/c8y c8y software list

# or exporting the env variable
export C8Y_HOST=http://localhost:8001/c8y
c8y software list