FunctionalJavascript tests cannot run while core excludes test modules from the package

CaptchaKeypadJavascriptTest fails on the next-major job with:

Unable to install modules captcha_keypad, js_testing_ajax_request_test,
js_testing_log_test, css_disable_transitions_test due to missing modules ...

Those three belong to Drupal core, and WebDriverTestBase installs them. Core
commit 5341dd83 on 2026-08-25, "task: #3067979 Exclude test files from release
packages", added modules/*/tests/*/ export-ignore to core/.gitattributes, so
they are no longer in the packaged drupal/core. Composer installs --prefer-dist
by default, so they never reach disk.

Confirmed by updating a Drupal 12 build to core dev-main: afterwards there are
no */tests/modules directories anywhere under web/core, while core's git tree
still has them. It affects core's own JavaScript tests and every contrib module
with a WebDriverTestBase test, so it is not specific to this module.

Nothing to change here. The job is allow_failure so it does not block anything,
and the tests will run again once core resolves it. Deliberately not skipping
them: the JavaScript tests are what caught the keypad being unusable in a
browser on Drupal 10 and later, and that coverage is worth keeping.

To close: once #3067979 is resolved, confirm CaptchaKeypadJavascriptTest runs
and passes on the next-major job.

Separately, the local drupalci containers have no chromedriver, so these tests
can only be run in CI at the moment. drupalci already documents a chromedriver
sidecar; wiring it into the Makefile would let them be run locally too.

See https://www.drupal.org/project/drupal/issues/3067979