Fix typo on tutorial-tic-tac-toe.md (#6843)

Change the tense of "build" to "building".

Author: skoryky

src/content/learn/tutorial-tic-tac-toe.md

@@ -2915,4 +2915,4 @@ If you have extra time or want to practice your new React skills, here are some
 1. When someone wins, highlight the three squares that caused the win (and when no one wins, display a message about the result being a draw).
 1. Display the location for each move in the format (row, col) in the move history list.
 
-Throughout this tutorial, you've touched on React concepts including elements, components, props, and state. Now that you've seen how these concepts work when building a game, check out [Thinking in React](/learn/thinking-in-react) to see how the same React concepts work when build an app's UI.
+Throughout this tutorial, you've touched on React concepts including elements, components, props, and state. Now that you've seen how these concepts work when building a game, check out [Thinking in React](/learn/thinking-in-react) to see how the same React concepts work when building an app's UI.