Remove trailing underscore

Resolves #1677

Author: swigof

books/RayTracingTheNextWeek.html

@@ -929,7 +929,7 @@
 traversal algorithm should be smooth and not have to check for null pointers, so if I just have one
 element I duplicate it in each subtree. Checking explicitly for three elements and just following
 one recursion would probably help a little, but I figure the whole method will get optimized later.
-The following code uses three methods--`box_x_compare`, `box_y_compare_`, and `box_z_compare`--that
+The following code uses three methods--`box_x_compare`, `box_y_compare`, and `box_z_compare`--that
 we haven't yet defined.
 
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