Simplify mtg in time management
Passed Stc:
LLR: 3.05 (-2.94,2.94) <-1.75,0.25>
Total: 289088 W: 74727 L: 74773 D: 139588
Ptnml(0-2): 903, 30974, 80841, 30918, 908
https://tests.stockfishchess.org/tests/view/699d9093eaae015cd278eda3
Passed Ltc:
LLR: 3.02 (-2.94,2.94) <-1.75,0.25>
Total: 144438 W: 36859 L: 36766 D: 70813
Ptnml(0-2): 62, 13391, 45235, 13454, 77
https://tests.stockfishchess.org/tests/view/699f02913ece4c464328a264
Passed Sudden death:
LLR: 2.99 (-2.94,2.94) <-1.75,0.25>
Total: 53406 W: 13960 L: 13753 D: 25693
Ptnml(0-2): 265, 5848, 14253, 6089, 248
https://tests.stockfishchess.org/tests/view/69a47548a70d5f3736be6482
closes https://github.com/official-stockfish/Stockfish/pull/6644
No functional change