Revert "Further increase safe checks bonus"

This reverts commit 4bc2374450 for
two reasons.

First regression testing shows almost equal
score:

Before the patch:
ELO: 49.75 +-2.5 (95%) LOS: 100.0%
Total: 27205 W: 7113 L: 3244 D: 16848

After the patch:
ELO: 48.87 +-2.9 (95%) LOS: 100.0%
Total: 20860 W: 5478 L: 2563 D: 12819

Second, and more sensible to me, this patch
increases safe check bonuses to 4 times their
original value (!) and considering:

- Values were already well tuned

- Values are highly critical

- King safety is highly critical, very TC
  dependent and very difficult to test

- Our testing coverage is partial (self-testing,
  blitz times)

I think is better to be safe than sorry and so
I revert the patch.

bench: 8440524

src/evaluate.cpp

@@ -200,12 +200,12 @@ namespace {
   const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
 
   // Bonuses for enemy's safe checks
-  const int QueenContactCheck = 24;
-  const int RookContactCheck  = 16;
-  const int QueenCheck        = 12;
-  const int RookCheck         = 8;
-  const int BishopCheck       = 2;
-  const int KnightCheck       = 3;
+  const int QueenContactCheck = 12;
+  const int RookContactCheck  = 8;
+  const int QueenCheck        = 6;
+  const int RookCheck         = 4;
+  const int BishopCheck       = 1;
+  const int KnightCheck       = 2;
 
   // KingExposed[Square] contains penalties based on the position of the
   // defending king, indexed by king's square (from white's point of view).