Bump @ember/test-helpers to ^4 in ember4 try scenarios

`min-supported` and `ember-lts-4.12` were failing in vite build with:

    [vite]: Rollup failed to resolve import "require" from
    ".../@ember/test-helpers/-internal/build-registry.js"

The line responsible is at the top of
`@ember/[email protected]/addon-test-support/@ember/test-helpers/-internal/build-registry.ts`:

    import require, { has } from 'require';

This is the AMD `require` module provided by classic Ember's loader.js.
When vite/rollup processes this file (after `@embroider/compat` rewrites
it into the addon's `rewritten-packages` tree), there is no `require`
module to resolve and the build fails.

`@ember/[email protected]` dropped that import and re-implemented
build-registry on top of `@ember/-internals/container` and
`./-owner-mixin-imports.js`, so it no longer depends on a loader.js-style
`require`. Its peer is `ember-source >= 4.0.0`, which satisfies both the
min-supported scenario (~4.2.0) and ember-lts-4.12. `ember-qunit@^8.0.0`
peers `@ember/test-helpers: >=3.0.3`, so the bump does not violate it.

Also bump `@ember/test-waiters` to `^3.1.0` to stay within the window
expected by test-helpers 4.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: NullVoxPopuli

test-app/.try.mjs

@@ -17,8 +17,8 @@ module.exports = async function (defaults) {
 };
 
   const ember4 = {
-    '@ember/test-helpers': '^3.2.1',
-    '@ember/test-waiters': '^3.0.0',
+    '@ember/test-helpers': '^4.0.0',
+    '@ember/test-waiters': '^3.1.0',
     '@embroider/compat': '^4.0.3',
     'ember-qunit': '^8.0.0',
     'ember-cli': '~4.12.0',