Temporarily disable Lox

The current lox_wasm.jsm import is broken (#43762 (closed)), and is likely out of date anyway. The 137 rebase basically commented out its import.

Until this is resolved, we should change LoxImpl.#enabled to false for the alpha channel, which will close off the Lox UI components, and avoid throwing errors. Maybe also for nightly/dev builds, unless we want the errors there as a reminder to fix this.

NOTE: If there happens to be an existing alpha user with Lox bridges, they will be lost with the update. Basically, the retrieval of the bridges will fail, so the user will be given the default bridge settings (none) instead for their session. If the user saves any proxy, firewall or bridges settings in the mean time, the underlying lox id preference will be wiped as well, and won't be restored when this is fixed.