Update test selenium launcher options

See https://github.com/dequelabs/axe-core/pull/5178

> Chrome-for-Testing downloaded fine but the browser wouldn't launch in my container — needed --no-sandbox and was missing the usual system libs (libnss3, libgbm, libasound2…). So I ran the same assertions through the jsdom path against the built axe.js instead. The two tests are in the normal browser suite though, so they'll run fine in your CI.
>
> If you want it smoother for container/CI folks, passing --no-sandbox --disable-dev-shm-usage in the launcher + a note on the apt deps would cover most headless setups.

Locate the Selenium launcher used by the normal browser suite and the two tests referenced in the issue; review how the suite runs against the built axe.js. Add the requested container-friendly launcher options and document the relevant apt dependencies, then verify the browser-suite assertions pass in CI.

Written by the indexing model from the issue text.