Remove javascript.options.large_arraybuffers

FF110+ 1703508 removed the pref javascript.options.large_arraybuffers

We set this to false (@pierov but not locked) when it was first added, because we do/did take steps to make it harder for scripts to detect the platform architecture (e.g. HTTP header / navigator), but this was more likely a consequence of reducing those metrics to a single result per platform

It is likely impossible to protect this metric (as pointed out by some moz engineers in email/bugzillas) ... but the pref @ true allowed for an extremely reliable and performant (5-10ms) test. We should decide if we want Tor Browser (or RFP) to patch this to make life hard for the b'stards