Update the mobile preset

[talktomedia-rob]

Feature request summary
Can the mobile preset speed be increased, it's an issue that has been raised and dismissed before

What is the motivation or use case for changing this?
The mobile landscape has changed dramatically over the last 3 years. The 85th percetile has to be higher than 1.6mbps

https://infrequently.org/2024/01/performance-inequality-gap-2024/#test-device-recommendations now suggests a Samsung Galaxy A51 or Google Pixel 4a as the benchmark, and a P75 estimate of 7.2Mbps down, 1.4Mbps up, and 94ms RTT.

How is this beneficial to Lighthouse?
It will bring the audit more in line with real world averages

[paulirish]

Thanks Rob. Alex's figures there are well researched and justified.