Simplify tm, removing faster 1st move and 1.13 extraTime.

Passed STC 10+0.1 :
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 349760 W: 90112 L: 90231 D: 169417
Ptnml(0-2): 784, 37970, 97496, 37841, 789
https://tests.stockfishchess.org/tests/view/665aeee00223e235f05b7d21

Passed LTC 60+0.6 :
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 140082 W: 35463 L: 35370 D: 69249
Ptnml(0-2): 59, 13492, 42851, 13575, 64
https://tests.stockfishchess.org/tests/view/665b15e78da109e362924e5a

closes https://github.com/official-stockfish/Stockfish/pull/5334

No functional change

src/timeman.cpp

@@ -48,7 +48,6 @@ void TimeManagement::init(Search::LimitsType& limits,
                           Color               us,
                           int                 ply,
                           const OptionsMap&   options,
-                          int&                originalPly,
                           double&             originalTimeAdjust) {
     TimePoint npmsec = TimePoint(options["nodestime"]);
 
@@ -60,9 +59,6 @@ void TimeManagement::init(Search::LimitsType& limits,
     if (limits.time[us] == 0)
         return;
 
-    if (originalPly == -1)
-        originalPly = ply;
-
     TimePoint moveOverhead = TimePoint(options["Move Overhead"]);
 
     // optScale is a percentage of available time to use for the current move.
@@ -104,20 +100,14 @@ void TimeManagement::init(Search::LimitsType& limits,
     TimePoint timeLeft = std::max(TimePoint(1), limits.time[us] + limits.inc[us] * (mtg - 1)
                                                   - moveOverhead * (2 + mtg));
 
-    // Extra time according to timeLeft
-    if (originalTimeAdjust < 0)
-        originalTimeAdjust = 0.2078 + 0.1623 * std::log10(timeLeft);
-
     // x basetime (+ z increment)
     // If there is a healthy increment, timeLeft can exceed the actual available
     // game time for the current move, so also cap to a percentage of available game time.
     if (limits.movestogo == 0)
     {
-        // Use extra time with larger increments
-        double optExtra = scaledInc < 500 ? 1.0 : 1.13;
-        if (ply - originalPly < 2)
-            optExtra *= 0.95;
-        optExtra *= originalTimeAdjust;
+        // Extra time according to timeLeft
+        if (originalTimeAdjust < 0)
+            originalTimeAdjust = 0.3285 * std::log10(timeLeft) - 0.4830;
 
         // Calculate time constants based on current time left.
         double logTimeInSec = std::log10(scaledTime / 1000.0);
@@ -126,7 +116,7 @@ void TimeManagement::init(Search::LimitsType& limits,
 
         optScale = std::min(0.0122 + std::pow(ply + 2.95, 0.462) * optConstant,
                             0.213 * limits.time[us] / timeLeft)
-                 * optExtra;
+                 * originalTimeAdjust;
 
         maxScale = std::min(6.64, maxConstant + ply / 12.0);
     }