Update osa1a.md

According to https://github.com/jsx-eslint/eslint-plugin-react/blob/master/docs/rules/prop-types.md, set "react/prop-types" to 0 to disable

Author: TheJiahao

src/content/1/fi/osa1a.md

@@ -391,7 +391,7 @@ module.exports = {
       'warn',
       { allowConstantExport: true },
     ],
-    'react/prop-types': false // highlight-line
+    'react/prop-types': 0 // highlight-line
   },
 }
 ```