fix(ws-head-latency-robinhood): QuickNode leads at 0.27ms, Alchemy 40ms, Chainstack 139ms

[Flotapponnier]

Update findings and FAQ on bench #244 to reflect live data:

• quicknode: p50 0.27ms — near-zero lag, wins the race across all 3 regions
• alchemy: p50 40ms — consistent across regions
• chainstack: p50 139ms — last despite being first to market with a dedicated node (HTTP bench tells a different story)