Drop unused init.h includes

These were entirely unused, as based on successful compilation
and a grep for:
  \bStartShutdown\(\)|\bShutdownRequested\(\)|\bInterrupt\(\)|\bShutdown\(\)|\bInitLogging\(\)|\bInitParameterInteraction\(\)|\bAppInitBasicSetup\(\)|\bAppInitParameterInteraction\(\)|\bAppInitSanityChecks\(\)|\bAppInitLockDataDirectory\(\)|\bAppInitMain\(\)|\bSetupServerArgs\(\)|\bLicenseInfo\(\)|g_wallet_init_interface|init.h

src/validationinterface.cpp

@@ -5,7 +5,6 @@
 
 #include <validationinterface.h>
 
-#include <init.h>
 #include <primitives/block.h>
 #include <scheduler.h>
 #include <sync.h>