Fix premature using of all available time in x/y TC

In x/y time controls there was a theoretical possibility
to use all available time few moves before the clock will
be updated with new time. This patch fixes that issue.

Tested at 60/15 time control:

LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 113963 W: 20008 L: 20042 D: 73913

The test was done without adjudication rules!

Bench 5234652

src/timeman.cpp

@@ -52,6 +52,9 @@ namespace {
         else
             ratio *= 1.5;
 
+        if (movesToGo > 1)
+            ratio = std::min(0.75, ratio);
+
         ratio *= 1 + inc / (myTime * 8.5);
     }
     // Otherwise we increase usage of remaining time as the game goes on