Fix missing variable 'm', which should be 'MLP_m'.

[ndahlquist]

NameError                                 Traceback (most recent call last)
<ipython-input-43-c13c6882f074> in <module>()
----> 1 dl,gl = train(MLP_D, MLP_G, m, 4000)

NameError: name 'm' is not defined

This is clearly intended to be MLP_m .

Test Plan

• After making this change, this part of the notebook works.