[request.md] Highlight that "The Firefox Data Collection Preference" is an acceptable option for Question 8

[chutten]

Question 8 reads "If this data collection is default on, what is the opt-out mechanism for users?"

The most common answer I want to see from people is "The Firefox Data Collection Preference" (because I get a lot of bog-standard Telemetry requests). Sometimes requesters are confused and ask if they need to implement something separate from the global telemetry opt-out if they're adding opt-out telemetry (they don't. Please don't do this.)

Shall we add this as a preferred/recommended option?

[fmarier]

Yes, please!

If we're going to provide a default option, let's use the exact wording from about:preferences and also include the equivalent about:config.