stop requesting mappings over the network

for some reason we're requesting the mappings.json file on every initial page load (and not cached in the shoebox). This is in the application afterModel hook so there is no chance that we will ever not make this request, so it's worth just backing the json into the JS bundle to save a request

app/services/legacy-module-mappings.js

@@ -1,7 +1,8 @@
-import fetch from 'fetch';
 import Service from '@ember/service';
 import { tracked } from '@glimmer/tracking';
 
+import mappings from 'ember-rfc176-data/mappings.json';
+
 const LOCALNAME_CONVERSIONS = {
   Object: 'EmberObject',
   Array: 'EmberArray',
@@ -13,8 +14,6 @@ export default class LegacyModuleMappingsService extends Service {
 
   async initMappings() {
     try {
-      let response = await this.fetch();
-      let mappings = await response.json();
       let newMappings = this.buildMappings(mappings);
       this.mappings = newMappings;
     } catch (e) {
@@ -32,10 +31,6 @@ export default class LegacyModuleMappingsService extends Service {
     });
   }
 
-  fetch() {
-    return fetch('/assets/mappings.json');
-  }
-
   getModule(name, documentedModule) {
     if (!this.mappings) {
       return '';

ember-cli-build.js

@@ -1,8 +1,6 @@
 'use strict';
 
 const EmberApp = require('ember-cli/lib/broccoli/ember-app');
-const Funnel = require('broccoli-funnel');
-const mergeTrees = require('broccoli-merge-trees');
 const envIsProduction = process.env.EMBER_ENV === 'production';
 const premberUrls = require('./prember-urls');
 const nodeSass = require('node-sass');
@@ -57,12 +55,6 @@ module.exports = function (defaults) {
     },
   });
 
-  let mappingsTree = new Funnel('node_modules/ember-rfc176-data/', {
-    srcDir: '/',
-    include: ['mappings.json'],
-    destDir: '/assets/',
-  });
-
   const { Webpack } = require('@embroider/webpack');
   const appTree = require('@embroider/compat').compatBuild(app, Webpack, {
     staticAddonTrees: true,
@@ -72,5 +64,5 @@ module.exports = function (defaults) {
     staticComponents: true,
   });
 
-  return mergeTrees([require('prember').prerender(app, appTree), mappingsTree]);
+  return require('prember').prerender(app, appTree);
 };

package.json

@@ -61,7 +61,6 @@
     "bourbon-neat": "^1.9.1",
     "broccoli-asset-rev": "^3.0.0",
     "broccoli-funnel": "^2.0.1",
-    "broccoli-merge-trees": "^2.0.0",
     "ember-a11y-testing": "^0.5.4",
     "ember-anchor": "^1.0.3",
     "ember-auto-import": "^2.7.2",