message: Add missing requires for chain_plugin
diff: #pragma once
  #include <appbase/application.hpp>
  #include <eosio/http_plugin/http_plugin.hpp>
  +#include <eosio/chain_plugin/chain_plugin.hpp>
  namespace eosio {
  @@ -15,7 +16,7 @@ public:
  txn_test_gen_plugin();
  ~txn_test_gen_plugin();
  - APPBASE_PLUGIN_REQUIRES((http_plugin))
  + APPBASE_PLUGIN_REQUIRES((http_plugin)(chain_plugin))
  virtual void set_program_options(options_description&, options_description& cfg) override;
  void plugin_initialize(const variables_map& options);
  