Drop unused boost::locale::generator instantiations

We now have one single case in gnc-locale-utils and all code
uses gnc_get_boost_locale to get the proper locale.

gnucash/import-export/csv-imp/assistant-csv-trans-import.cpp

@@ -2094,11 +2094,6 @@ CsvImpTransAssist::assist_summary_page_prepare ()
     gtk_assistant_remove_action_widget (csv_imp_asst, help_button);
     gtk_assistant_remove_action_widget (csv_imp_asst, cancel_button);
 
-    // FIXME Rather than passing a locale generator below we probably should set std::locale::global appropriately somewhere.
-    bl::generator gen;
-    gen.add_messages_path(gnc_path_get_localedir());
-    gen.add_messages_domain(PROJECT_NAME);
-
     auto text = std::string("<span size=\"medium\"><b>");
     try
     {

libgnucash/core-utils/gnc-filepath-utils.cpp

@@ -589,10 +589,6 @@ static std::string migrate_gnc_datahome()
     bfs::path old_dir(g_get_home_dir(), cvt);
     old_dir /= ".gnucash";
 
-    bl::generator gen;
-    gen.add_messages_path(gnc_path_get_datadir());
-    gen.add_messages_domain(PROJECT_NAME);
-
     std::stringstream migration_msg;
     migration_msg.imbue(gnc_get_boost_locale());