Remove SlowMover Option

The SlowMover option allows users to modify the timeLeft variant, impacting the
engine's time management. However, this feature, while theoretically flexible,
doesn't offer substantial benefits. Instead, it introduces the risk of
non-experienced users altering values without a clear understanding of the
effects, potentially leading to a weaker engine.

The vast majority of SF users don't use it anyway, and based on tests conducted
by fauzi several months ago suggest that changing it would only lose Elo.

Examples:
https://tests.stockfishchess.org/tests/view/651f309bac57711436726bba
https://tests.stockfishchess.org/tests/view/651fea29ac57711436727d85
https://tests.stockfishchess.org/tests/view/65257c343125598fc7eb68a1
https://tests.stockfishchess.org/tests/view/652296c83125598fc7eb2ad7
Tune:
https://tests.stockfishchess.org/tests/view/652a70313125598fc7ebd706
(keeping the value at 100, zz2)

closes #4917

No functional change

src/timeman.cpp

@@ -42,7 +42,6 @@ void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
         return;
 
     TimePoint moveOverhead = TimePoint(Options["Move Overhead"]);
-    TimePoint slowMover    = TimePoint(Options["Slow Mover"]);
     TimePoint npmsec       = TimePoint(Options["nodestime"]);
 
     // optScale is a percentage of available time to use for the current move.
@@ -78,10 +77,6 @@ void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
     double optConstant = std::min(0.00335 + 0.0003 * std::log10(limits.time[us] / 1000.0), 0.0048);
     double maxConstant = std::max(3.6 + 3.0 * std::log10(limits.time[us] / 1000.0), 2.7);
 
-    // A user may scale time usage by setting UCI option "Slow Mover"
-    // Default is 100 and changing this value will probably lose elo.
-    timeLeft = slowMover * timeLeft / 100;
-
     // x basetime (+ z increment)
     // If there is a healthy increment, timeLeft can exceed actual available
     // game time for the current move, so also cap to 20% of available game time.

src/ucioption.cpp

@@ -73,7 +73,6 @@ void init(OptionsMap& o) {
     o["MultiPV"] << Option(1, 1, 500);
     o["Skill Level"] << Option(20, 0, 20);
     o["Move Overhead"] << Option(10, 0, 5000);
-    o["Slow Mover"] << Option(100, 10, 1000);
     o["nodestime"] << Option(0, 0, 10000);
     o["UCI_Chess960"] << Option(false);
     o["UCI_AnalyseMode"] << Option(false);