fix: typo in lesson 19 (#578)

Author: pcamp

course/lesson-19-creating-arrays/lesson.tres

@@ -161,7 +161,7 @@ text = "Let's look at a widespread use of arrays in games: finding and following
 
 In games, you need allies or monsters to find their way to their target, whether it's the player or some point of interest.
 
-To achieve that, we use [i]pathfinding algorithms[/i]. As a name suggests, those algorithms find the path between two points and allow AIs to traverse the game."
+To achieve that, we use [i]pathfinding algorithms[/i]. As the name suggests, those algorithms find the path between two points and allow AIs to traverse the game."
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