Simplification: Remove the ply-5 continuation history update
Simplification: The ply-5 continuation history update was added in #5792 together with a matching read in move ordering. #5978 removed that read as a simplification but kept the update, which has the smallest weight of any ply (66). This patch removes the ply-5 update too and drops the last CMHC multiplier which is no longer reachable.
Passed STC non-reg:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 27904 W: 7221 L: 7000 D: 13683
Ptnml(0-2): 25, 3171, 7350, 3370, 36
https://tests.stockfishchess.org/tests/view/6ac40de55349156614d93bbd
Passed LTC non-reg:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 74304 W: 19085 L: 18923 D: 36296
Ptnml(0-2): 10, 7765, 21442, 7923, 12
https://tests.stockfishchess.org/tests/view/6ac4cb435349156614d93c6b
closes https://github.com/official-stockfish/Stockfish/pull/7212
Bench: 1334778