Flex output: Remove code that alters table in append mode

This code was basically copied over from the pgsql output. It is a
half-measure that can detect some needed changes in your database tables
when you change the config after import. But this was never tested
properly and what is implemented is not enough to make this a useful
feature. So lets get rid of it.

Author: joto

src/flex-table.cpp

@@ -167,25 +167,6 @@ void table_connection_t::start(bool append)
             table().has_geom_column() ? flex_table_t::table_type::interim
                                       : flex_table_t::table_type::permanent,
             table().full_name()));
-    } else {
-        //check the columns against those in the existing table
-        auto const res = m_db_connection->query(
-            PGRES_TUPLES_OK,
-            "SELECT * FROM {} LIMIT 0"_format(table().full_name()));
-
-        for (auto const &column : table()) {
-            if (res.get_column_number(column.name()) < 0) {
-                log_info("Adding new column '{}' to '{}'", column.name(),
-                         table().name());
-                m_db_connection->exec(
-                    "ALTER TABLE {} ADD COLUMN \"{}\" {}"_format(
-                        table().full_name(), column.name(),
-                        column.sql_type_name()));
-            }
-            // Note: we do not verify the type or delete unused columns
-        }
-
-        //TODO: change the type of the geometry column if needed - this can only change to a more permissive type
     }
 
     prepare();