refactor: inline constant return value of `BlockTreeDB::WriteBatchSync` and `BlockManager::WriteBlockIndexDB` and `BlockTreeDB::WriteFlag`

diff --git a/src/node/blockstorage.cpp b/src/node/blockstorage.cpp
index 5a54baf2..a72292cb 100644
--- a/src/node/blockstorage.cpp
+++ b/src/node/blockstorage.cpp
@@ -78,7 +78,7 @@ bool BlockTreeDB::ReadLastBlockFile(int& nFile)
     return Read(DB_LAST_BLOCK, nFile);
 }
 
-bool BlockTreeDB::WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo)
+void BlockTreeDB::WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo)
 {
     CDBBatch batch(*this);
     for (const auto& [file, info] : fileInfo) {
@@ -89,13 +89,11 @@ bool BlockTreeDB::WriteBatchSync(const std::vector<std::pair<int, const CBlockFi
         batch.Write(std::make_pair(DB_BLOCK_INDEX, bi->GetBlockHash()), CDiskBlockIndex{bi});
     }
     WriteBatch(batch, true);
-    return true;
 }
 
-bool BlockTreeDB::WriteFlag(const std::string& name, bool fValue)
+void BlockTreeDB::WriteFlag(const std::string& name, bool fValue)
 {
     Write(std::make_pair(DB_FLAG, name), fValue ? uint8_t{'1'} : uint8_t{'0'});
-    return true;
 }
 
 bool BlockTreeDB::ReadFlag(const std::string& name, bool& fValue)
@@ -478,7 +476,7 @@ bool BlockManager::LoadBlockIndex(const std::optional<uint256>& snapshot_blockha
     return true;
 }
 
-bool BlockManager::WriteBlockIndexDB()
+void BlockManager::WriteBlockIndexDB()
 {
     AssertLockHeld(::cs_main);
     std::vector<std::pair<int, const CBlockFileInfo*>> vFiles;
@@ -494,10 +492,7 @@ bool BlockManager::WriteBlockIndexDB()
         m_dirty_blockindex.erase(it++);
     }
     int max_blockfile = WITH_LOCK(cs_LastBlockFile, return this->MaxBlockfileNum());
-    if (!m_block_tree_db->WriteBatchSync(vFiles, max_blockfile, vBlocks)) {
-        return false;
-    }
-    return true;
+    m_block_tree_db->WriteBatchSync(vFiles, max_blockfile, vBlocks);
 }
 
 bool BlockManager::LoadBlockIndexDB(const std::optional<uint256>& snapshot_blockhash)
diff --git a/src/node/blockstorage.h b/src/node/blockstorage.h
index 7d6f78f2..caf291e9 100644
--- a/src/node/blockstorage.h
+++ b/src/node/blockstorage.h
@@ -52,12 +52,12 @@ class BlockTreeDB : public CDBWrapper
 {
 public:
     using CDBWrapper::CDBWrapper;
-    bool WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo);
+    void WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo);
     bool ReadBlockFileInfo(int nFile, CBlockFileInfo& info);
     bool ReadLastBlockFile(int& nFile);
     void WriteReindexing(bool fReindexing);
     void ReadReindexing(bool& fReindexing);
-    bool WriteFlag(const std::string& name, bool fValue);
+    void WriteFlag(const std::string& name, bool fValue);
     bool ReadFlag(const std::string& name, bool& fValue);
     bool LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex, const util::SignalInterrupt& interrupt)
         EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
@@ -300,7 +300,7 @@ public:
 
     std::unique_ptr<BlockTreeDB> m_block_tree_db GUARDED_BY(::cs_main);
 
-    bool WriteBlockIndexDB() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
+    void WriteBlockIndexDB() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
     bool LoadBlockIndexDB(const std::optional<uint256>& snapshot_blockhash)
         EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
diff --git a/src/test/fuzz/block_index.cpp b/src/test/fuzz/block_index.cpp
index eef8c2ef..5bc6240c 100644
--- a/src/test/fuzz/block_index.cpp
+++ b/src/test/fuzz/block_index.cpp
@@ -89,7 +89,7 @@ FUZZ_TARGET(block_index, .init = init_block_index)
     }
 
     // Store these files and blocks in the block index. It should not fail.
-    assert(block_index.WriteBatchSync(files_info, files_count - 1, blocks_info));
+    block_index.WriteBatchSync(files_info, files_count - 1, blocks_info);
 
     // We should be able to read every block file info we stored. Its value should correspond to
     // what we stored above.
diff --git a/src/validation.cpp b/src/validation.cpp
index 7b7c8b2d..c3221185 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2851,9 +2851,7 @@ bool Chainstate::FlushStateToDisk(
             {
                 LOG_TIME_MILLIS_WITH_CATEGORY("write block index to disk", BCLog::BENCH);
 
-                if (!m_blockman.WriteBlockIndexDB()) {
-                    return FatalError(m_chainman.GetNotifications(), state, _("Failed to write to block index database."));
-                }
+                m_blockman.WriteBlockIndexDB();
             }
             // Finally remove any pruned files
             if (fFlushForPrune) {