Fix typo on aspect ratio page

Summary: Was reading https://yogalayout.com/docs/aspect-ratio and noticed a typo. "Flexbox does has" -> "Flexbox does have"

Reviewed By: NickGerleman

Differential Revision: D49885138

fbshipit-source-id: 847b40eda257bd0726c3992a7285ac6fa267d418

website/contents/properties/aspect-ratio.md

@@ -7,7 +7,7 @@ hasPlayground: true
 ## Aspect Ratio
 
 AspectRatio is a property introduced by Yoga and is not present as a settable
-property in the css flexbox specification. Flexbox does has the notion of
+property in the css flexbox specification. Flexbox does have the notion of
 aspect ratio though for things with intrinsic aspect ratio such as images.
 
 The `aspect ratio` property in Yoga has the following properties: