Use tor-expert-bundle-aar in geckoview/build_apk

For #41123 (closed) and after the monorepo migration, I moved all the steps to build Fenix inside GeckoView, in what we used to call merge_aars and now call build_apk.

However, since we didn't have our Android patchset yet, I didn't know where to place tor-expert-bundle.aar. But now that we have our patches, we need it.