fix: remove Gatsby proxy (#37364)

Direct ajax calls to the server directly, rather than a proxy to reduce
redirects while still allowing the server to be used in development.

client/gatsby-config.js

@@ -6,8 +6,6 @@ const {
   localeChallengesRootDir
 } = require('./utils/buildChallenges');
 
-const { API_PROXY: proxyUrl = 'http://localhost:3000' } = process.env;
-
 const curriculumIntroRoot = path.resolve(__dirname, './src/pages');
 
 module.exports = {
@@ -15,10 +13,6 @@ module.exports = {
     title: 'freeCodeCamp',
     siteUrl: 'https://www.freecodecamp.org'
   },
-  proxy: {
-    prefix: '/internal',
-    url: proxyUrl
-  },
   plugins: [
     'gatsby-plugin-react-helmet',
     'gatsby-plugin-postcss',