Update tutorial.md (#2115)

changed 'any React apps' to 'any React app'

content/tutorial/tutorial.md

@@ -16,7 +16,7 @@ This tutorial doesn't assume any existing React knowledge.
 
 ## Before We Start the Tutorial {#before-we-start-the-tutorial}
 
-We will build a small game during this tutorial. **You might be tempted to skip it because you're not building games -- but give it a chance.** The techniques you'll learn in the tutorial are fundamental to building any React apps, and mastering it will give you a deep understanding of React.
+We will build a small game during this tutorial. **You might be tempted to skip it because you're not building games -- but give it a chance.** The techniques you'll learn in the tutorial are fundamental to building any React app, and mastering it will give you a deep understanding of React.
 
 >Tip
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