Remove useless condition

Small simplification, suggested by Uri Blass.

passed STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 25839 W: 4464 L: 4351 D: 17024

and LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 220039 W: 29981 L: 30131 D: 159927

No functional change.
Merge branch 'master' of https://github.com/official-stockfish/Stockfish