Eliminate use of wp_service_worker_json_encode()

[westonruter]

The wp_service_worker_json_encode() function was added to automatically strip slashes and pretty-print. This was for the sake of manually inspecting the service worker JS. However, this adds additional bytes to the response. And in practice, pretty-printing is easily done in DevTools anyway.

So I want to eliminate the use of wp_service_worker_json_encode(). We can just remove it since no other plugins are using this function, but to be safe we can deprecate it.