Update relevant gallery images

Author: scottshambaugh

examples/mplot3d/surface3d_2.py

@@ -23,4 +23,7 @@
 # Plot the surface
 ax.plot_surface(x, y, z)
 
+# Set an equal aspect ratio
+ax.set_aspect('equal')
+
 plt.show()

examples/mplot3d/voxels_numpy_logo.py

@@ -42,5 +42,6 @@ def explode(data):
 
 ax = plt.figure().add_subplot(projection='3d')
 ax.voxels(x, y, z, filled_2, facecolors=fcolors_2, edgecolors=ecolors_2)
+ax.set_aspect('equal')
 
 plt.show()

examples/mplot3d/voxels_rgb.py

@@ -39,5 +39,6 @@ def midpoints(x):
           edgecolors=np.clip(2*colors - 0.5, 0, 1),  # brighter
           linewidth=0.5)
 ax.set(xlabel='r', ylabel='g', zlabel='b')
+ax.set_aspect('equal')
 
 plt.show()