Use latest ember-cli beta version in CI

CI currently fails the typescript tests, due to a known issue that the latest stable version (4.9.x) of ember-cli support `--typescript`, but a fix when generating the app in a custom directory (ember-cli/ember-cli#10048) is only released for the 4.10.0-beta version. Se we use the latter in CI.

.github/workflows/ci.yml

@@ -51,6 +51,6 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - uses: ./.github/actions/pnpm
-      - run: pnpm add --global ember-cli yarn
+      - run: pnpm add --global ember-cli@beta yarn
       - run: pnpm vitest --testNamePattern "${{ matrix.slow-test }}"
         working-directory: tests