Set witness cache size equal to coinbase maturity duration

Both constants have the same implicit assumption: that the blockchain will very
rarely undergo a reorganisation of that size.

src/wallet/wallet.cpp

@@ -8,7 +8,6 @@
 #include "base58.h"
 #include "checkpoints.h"
 #include "coincontrol.h"
-#include "consensus/consensus.h"
 #include "consensus/validation.h"
 #include "init.h"
 #include "main.h"