use correct function in React querying example; add missing dependency (#206)

Author: stefan-girlich

pages/en/querying/querying-from-an-application.mdx

@@ -109,13 +109,13 @@ import React, { useEffect } from 'react'
 import { ExampleQueryDocument, ExampleQueryQuery, execute } from '../.graphclient'
 
 function App() {
-  const [data, setData] = React.useState<ExampleQueryQuery>()
+  const [result, setResult] = React.useState<ExampleQueryQuery>()
 
   useEffect(() => {
     execute(ExampleQueryDocument, {}).then((result) => {
       setData(result?.data)
     })
-  }, [])
+  }, [setResult])
   return (
     <div className="App">
       <header className="App-header">