Update dcgan_faces_tutorial.py (pytorch#1550)

Co-authored-by: Holly Sweeney <77758406+holly1238@users.noreply.github.com>

beginner_source/dcgan_faces_tutorial.py

@@ -52,7 +52,7 @@
 # with the discriminator. Let :math:`x` be data representing an image.
 # :math:`D(x)` is the discriminator network which outputs the (scalar)
 # probability that :math:`x` came from training data rather than the
-# generator. Here, since we are dealing with images the input to
+# generator. Here, since we are dealing with images, the input to
 # :math:`D(x)` is an image of CHW size 3x64x64. Intuitively, :math:`D(x)`
 # should be HIGH when :math:`x` comes from training data and LOW when
 # :math:`x` comes from the generator. :math:`D(x)` can also be thought of