TypeError when using adrf neurons

[felixthoe]

Describe the bug
There seems to be a small bug in the implementation of the adrf neuron (lava-dl/src/lib/dl/slayer/neuron/adrf.py). The Neuron.forward() function calls self.spike(real, imag, threshold + refractory), while it should be self.spike(real, imag, threshold, refractory) according to the definition of the function Neuron.spike() in the same file.

To reproduce current behavior
Steps to reproduce the behavior:

1. When I run this code...

import lava.lib.dl.slayer as slayer
import torch
# choose arbitrary neuron parameters
my_neuron = slayer.neuron.adrf.Neuron(
    threshold = 1,
    threshold_step = 0.2,
    period = 4,
    decay = 0.3,
    threshold_decay = 0.3,
    refractory_decay = 0.3
    )
# some random, complex input of shape ((N,C,T),(N,C,T))
input = (torch.randn((16, 10, 50)), torch.randn((16,10,50)))
output = my_neuron(input)

2. I get this error ...

 File "/home/ujrrg/miniconda3/envs/lava/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1501, in _call_impl
    return forward_call(*args, **kwargs)
  File "/home/ujrrg/miniconda3/envs/lava/lib/python3.9/site-packages/lava/lib/dl/slayer/neuron/adrf.py", line 677, in forward
    return self.spike(real, imag, threshold + refractory)
TypeError: spike() missing 1 required positional argument: 'refractory'

[PhilippPlank]

Great catch. Feel free to create a pull request for this fix :)