Fix typo

Author: Hofer-Julian

books/RayTracingInOneWeekend.html

@@ -219,7 +219,7 @@
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 Almost all graphics programs have some class(es) for storing geometric vectors and colors. In many
 systems these vectors are 4D (3D plus a homogeneous coordinate for geometry, and RGB plus an alpha
-transparency channel for colors). For our purposes, three coordinates suffices. We’ll use the same
+transparency channel for colors). For our purposes, three coordinates suffice. We’ll use the same
 class `vec3` for colors, locations, directions, offsets, whatever. Some people don’t like this
 because it doesn’t prevent you from doing something silly, like adding a color to a location. They
 have a good point, but we’re going to always take the “less code” route when not obviously wrong.