refactor: Replace validation.h include with forward-decl in miner.h

Author: MarcoFalke

src/node/miner.cpp

@@ -21,6 +21,7 @@
 #include <timedata.h>
 #include <util/moneystr.h>
 #include <util/system.h>
+#include <validation.h>
 
 #include <algorithm>
 #include <utility>

src/node/miner.h

@@ -8,15 +8,15 @@
 
 #include <primitives/block.h>
 #include <txmempool.h>
-#include <validation.h>
 
 #include <memory>
 #include <optional>
 #include <stdint.h>
 
-#include <boost/multi_index_container.hpp>
 #include <boost/multi_index/ordered_index.hpp>
+#include <boost/multi_index_container.hpp>
 
+class ChainstateManager;
 class CBlockIndex;
 class CChainParams;
 class CScript;