Fix ThemeContext usage in MyApp component

Author: nannany

src/content/reference/react/Component.md

@@ -1814,9 +1814,9 @@ function Form() {
 
 export default function MyApp() {
   return (
-    <ThemeContext.Provider value="dark">
+    <ThemeContext value="dark">
       <Form />
-    </ThemeContext.Provider>
+    </ThemeContext>
   )
 }
 ```
@@ -1900,9 +1900,9 @@ function Form() {
 
 export default function MyApp() {
   return (
-    <ThemeContext.Provider value="dark">
+    <ThemeContext value="dark">
       <Form />
-    </ThemeContext.Provider>
+    </ThemeContext>
   )
 }
 ```