Drop ember-qunit support below v5

The scenario wasn't working with ember-cli@5 and ember-qunit has been out
for a while.

.github/workflows/ci.yml

@@ -56,7 +56,6 @@ jobs:
           - ember-release
           - ember-beta
           - ember-canary
-          - ember-qunit-4
 
     steps:
       - uses: actions/checkout@v2

index.js

@@ -2,8 +2,6 @@
 
 'use strict';
 
-const VersionChecker = require('ember-cli-version-checker');
-
 module.exports = {
   name: require('./package').name,
 
@@ -13,30 +11,9 @@ module.exports = {
 
   init() {
     this._super.init.apply(this, arguments);
-    let versionChecker = new VersionChecker(this.project);
-
-    const hasMagicallyProvidedQUnit = versionChecker
-      .for('ember-qunit')
-      .lt('5.0.0-beta.1');
 
-    let options = {
+    this.options.autoImport = {
       exclude: ['ember-mocha', 'mocha'],
     };
-
-    // Ember-qunit < 5 provides an AMD shim for qunit but newer versions now use
-    // ember-auto-import to include qunit. This means that qunit is no
-    // longer available for addons (if the parent app is using ember-qunit > 5) to
-    // directly import under embroider unless they are using ember-auto-import
-    // themselves. This condidionally falls back to not using ember-auto-import
-    // when the parent app is providing qunit because without this we would double
-    // include qunit resulting in a runtime error (qunit detects if it as
-    // already be added to the window object and errors if so).
-    if (hasMagicallyProvidedQUnit) {
-      this.options = this.options || {};
-      options.exclude.push('qunit');
-      this.options.autoImport = options;
-    } else {
-      this.options.autoImport = options;
-    }
   },
 };

package.json

@@ -46,7 +46,6 @@
     "debug": "^4.2.0",
     "ember-auto-import": "^2.7.0",
     "ember-cli-babel": "^8.2.0",
-    "ember-cli-version-checker": "^5.1.2",
     "execa": "^8.0.1",
     "fs-extra": "^11.2.0",
     "js-yaml": "^4.0.0",

tests/dummy/config/ember-try.js

@@ -120,15 +120,6 @@ module.exports = async function () {
           name: 'embroider-optimized-with-mocha',
         }),
       ),
-      {
-        name: 'ember-qunit-4',
-        npm: {
-          devDependencies: {
-            'ember-qunit': '^4.6.0',
-            'ember-source': '^3.28.0',
-          },
-        },
-      },
     ],
   };
 };