sql: fix minor typo in plan_opt.go

Release note: None

pkg/sql/plan_opt.go

@@ -1032,7 +1032,7 @@ func (opc *optPlanningCtx) makeQueryIndexRecommendation(
 	// Save the normalized memo created by the optbuilder.
 	savedMemo := opc.optimizer.DetachMemo(ctx)
 
-	// Use the optimizer to fully normalize the memo. We need to do this before
+	// Use the optimizer to fully optimize the memo. We need to do this before
 	// finding index candidates because the *memo.SortExpr from the sort enforcer
 	// is only added to the memo in this step. The sort expression is required to
 	// determine certain index candidates.