refactoring: remove unused chainActive

src/validation.cpp

@@ -235,7 +235,6 @@ CChain& ChainActive() { return g_chainstate.m_chain; }
 RecursiveMutex cs_main;
 
 BlockMap& mapBlockIndex = g_chainstate.mapBlockIndex;
-CChain& chainActive = g_chainstate.m_chain;
 CBlockIndex *pindexBestHeader = nullptr;
 Mutex g_best_block_mutex;
 std::condition_variable g_best_block_cv;

src/validation.h

@@ -435,9 +435,6 @@ bool InvalidateBlock(CValidationState& state, const CChainParams& chainparams, C
 /** Remove invalidity status from a block and its descendants. */
 void ResetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
-/** The currently-connected chain of blocks (protected by cs_main). */
-extern CChain& chainActive;
-
 /** @returns the most-work chain. */
 CChain& ChainActive();