refactor: inline constant return value of CDBWrapper::WriteBatch

`WriteBatch` can only ever return `true` - its errors are handled by throwing a `throw dbwrapper_error` instead.
The boolean return value is quite confusing, especially since it's symmetric with `CDBWrapper::Read`, which catches the exceptions and returns a boolean instead.
We're removing the constant return value and inlining `true` for its usages.

src/index/base.cpp

@@ -262,7 +262,7 @@ bool BaseIndex::Commit()
         ok = CustomCommit(batch);
         if (ok) {
             GetDB().WriteBestBlock(batch, GetLocator(*m_chain, m_best_block_index.load()->GetBlockHash()));
-            ok = GetDB().WriteBatch(batch);
+            GetDB().WriteBatch(batch);
         }
     }
     if (!ok) {