Update 02.1-jsx-in-depth.md

Update 02.1-jsx-in-depth.md

docs/02.1-jsx-in-depth.md

@@ -22,7 +22,7 @@ It doesn't alter the semantics of JavaScript.
 
 React can either render HTML tags (strings) or React components (classes).
 
-To render a HTML tag, just use lower-case tag names in JSX:
+To render an HTML tag, just use lower-case tag names in JSX:
 
 ```javascript
 var myDivElement = <div className="foo" />;