docs: drop the stale FUTURE comment from performance.md

Author: daveedis

docs/performance.md

@@ -1,10 +1,3 @@
-<!-- FUTURE: numbers below are single-machine direction checks (WSL2, PHP
-     8.1, opcache on, xdebug off), all produced by the one command in
-     "Reproducing the Numbers". SmartArray's per-operation numbers and the
-     encoding claims already run on SmartString's CI speed matrix; only the
-     whole-page numbers here are local. We may add a CI workflow to re-run
-     them across a platform matrix, like SmartString's page. -->
-
 # Performance: What SmartArray Costs vs Plain Arrays
 
 SmartArray is extremely fast by default. At worst, wrapping a 25-row query