removed duplicated word (#449)

Author: mahezsh

pages/docs/react/latest/components-and-props.mdx

@@ -144,7 +144,7 @@ var greeting = React.createElement(Playground$Greeting, tmp);
 
 ### Special Props `key` and `ref`
 
-You can't define any props called `key` or `ref`. React treats those props differently and the compiler will will yield an error whenever you try to define a `~key` or `~ref` argument in your component function.
+You can't define any props called `key` or `ref`. React treats those props differently and the compiler will yield an error whenever you try to define a `~key` or `~ref` argument in your component function.
 
 Check out the corresponding [Arrays and Keys](./arrays-and-keys) and [Forwarding React Refs](./forwarding-refs) sections for more details.