Tweak losing chess NMP reduction

giveaway STC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 2636 W: 1055 L: 937 D: 644
http://www.variantfishtest.org:6543/tests/view/5ff074aa6e23db221d9e983e

giveaway LTC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 1224 W: 503 L: 405 D: 316
http://www.variantfishtest.org:6543/tests/view/5ff0d5056e23db221d9e9847

losers STC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 1856 W: 882 L: 763 D: 211
http://www.variantfishtest.org:6543/tests/view/5ff08fe96e23db221d9e9843

losers LTC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 2315 W: 1067 L: 943 D: 305
http://www.variantfishtest.org:6543/tests/view/5ff0d4f66e23db221d9e9845

src/search.cpp

@@ -943,7 +943,7 @@ namespace {
         assert(eval - beta >= 0);
 
         // Null move dynamic reduction based on depth and value
-        Depth R = (1015 - 200 * pos.must_capture() - 150 * !pos.checking_permitted() + 85 * depth) / 256 + std::min(int(eval - beta) / 191, 3);
+        Depth R = (1015 - 300 * pos.must_capture() - 150 * !pos.checking_permitted() + 85 * depth) / 256 + std::min(int(eval - beta) / 191, 3);
 
         ss->currentMove = MOVE_NULL;
         ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];