update help

book/src/help_bn.md

@@ -385,10 +385,8 @@ OPTIONS:
             useful for execution nodes which don't improve their payload after the first call, and high values are
             useful for ensuring the EL is given ample notice. Default: 1/3 of a slot.
         --progressive-balances <MODE>
-            Control the progressive balances cache mode. The default `fast` mode uses the cache to speed up fork choice.
-            A more conservative `checked` mode compares the cache's results against results without the cache. If there
-            is a mismatch, it falls back to the cache-free result. Using the default `fast` mode is recommended unless
-            advised otherwise by the Lighthouse team. [possible values: disabled, checked, strict, fast]
+            Deprecated. This optimisation is now the default and cannot be disabled. [possible values: fast, disabled,
+            checked, strict]
         --proposer-reorg-cutoff <MILLISECONDS>
             Maximum delay after the start of the slot at which to propose a reorging block. Lower values can prevent
             failed reorgs by ensuring the block has ample time to propagate and be processed by the network. The default