🐛 Revert "🐛 Detect threefold repetition on pvNode (#796)"

[eduherminio]

This reverts commit 49b926f.

This is an attempt to fix Lynx 1.5.0 inability to convert some completely won endgames, allowing threefold repetitions instead.
Concrete examples:

• https://lichess.org/XB4q079W/white#135
• https://lichess.org/F0VcRwsn/black#163
• https://lichess.org/48ylW0sA/black#129
• https://lichess.org/MpHsNLVL/white#138
• https://lichess.org/qyzvj68s/black
• https://lichess.org/puU6wF11/white
• https://lichess.org/WEI9JMJL/white
• https://lichess.org/K1iROCRy/white
• https://lichess.org/NUjmzsYJ/black#263

No adjudication/draws:

Test  | revert-threefold-pvnode
Elo   | 23.54 +- 10.96 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=32MB
LLR   | 2.91 (-2.25, 2.89) [0.00, 5.00]
Games | 2188: +692 -544 =952
Penta | [42, 232, 428, 320, 72]
https://openbench.lynx-chess.com/test/406/

with adjudication/draws

Score of Lynx-revert-threefold-pvnode-3179-win-x64 vs Lynx 3164 - main: 5574 - 5287 - 6256  [0.508] 17117
...      Lynx-revert-threefold-pvnode-3179-win-x64 playing White: 3853 - 1590 - 3116  [0.632] 8559
...      Lynx-revert-threefold-pvnode-3179-win-x64 playing Black: 1721 - 3697 - 3140  [0.385] 8558
...      White vs Black: 7550 - 3311 - 6256  [0.624] 17117
Elo difference: 5.8 +/- 4.1, LOS: 99.7 %, DrawRatio: 36.5 %
SPRT: llr 2.9 (100.3%), lbound -2.25, ubound 2.89 - H1 was accepted

40+0.4, 256MB, no adj/draws

Score of Lynx-revert-threefold-pvnode-3179-win-x64 vs Lynx 3164 - main: 1553 - 1352 - 2583  [0.518] 5488
...      Lynx-revert-threefold-pvnode-3179-win-x64 playing White: 1180 - 338 - 1227  [0.653] 2745
...      Lynx-revert-threefold-pvnode-3179-win-x64 playing Black: 373 - 1014 - 1356  [0.383] 2743
...      White vs Black: 2194 - 711 - 2583  [0.635] 5488
Elo difference: 12.7 +/- 6.7, LOS: 100.0 %, DrawRatio: 47.1 %
SPRT: llr 2.9 (100.2%), lbound -2.25, ubound 2.89 - H1 was accepted

40+0.4, 32MB, no adj/draws

Score of Lynx-revert-threefold-pvnode-3179-win-x64 vs Lynx 3164 - main: 1061 - 864 - 1620  [0.528] 3545
...      Lynx-revert-threefold-pvnode-3179-win-x64 playing White: 816 - 200 - 756  [0.674] 1772
...      Lynx-revert-threefold-pvnode-3179-win-x64 playing Black: 245 - 664 - 864  [0.382] 1773
...      White vs Black: 1480 - 445 - 1620  [0.646] 3545
Elo difference: 19.3 +/- 8.4, LOS: 100.0 %, DrawRatio: 45.7 %
SPRT: llr 2.9 (100.3%), lbound -2.25, ubound 2.89 - H1 was accepted