Remove --column-statistics for MariaDB schema dump

When `php artisan schema:dump` is run with a MariaDB connection, the
warning message `mysqldump: unknown variable 'column-statistics=0'`
appears, but the dump is otherwise successful.

This is because the `--column-statistics` flag is MySQL specific, and
does not exist in MariaDB's version of `mysqldump`.

Let's remove the `--column-statistics` flag from the `schema:dump`
command when it is run against a MariaDB connection.

There should be no issues with removing the flag in MariaDB as the flag
has no effect otherwise and `schema:dump` still functions correctly
with MariaDB even with the flag removed.

src/Illuminate/Database/Schema/MySqlSchemaState.php

@@ -81,9 +81,10 @@ public function load($path)
      */
     protected function baseDumpCommand()
     {
+        $columnStatistics = $this->connection->isMaria() ? '' : '--column-statistics=0';
         $gtidPurged = $this->connection->isMaria() ? '' : '--set-gtid-purged=OFF';
 
-        return 'mysqldump '.$gtidPurged.' --column-statistics=0 --skip-add-drop-table --skip-add-locks --skip-comments --skip-set-charset --tz-utc --host="${:LARAVEL_LOAD_HOST}" --port="${:LARAVEL_LOAD_PORT}" --user="${:LARAVEL_LOAD_USER}" --password="${:LARAVEL_LOAD_PASSWORD}" "${:LARAVEL_LOAD_DATABASE}"';
+        return 'mysqldump '.$gtidPurged.' '.$columnStatistics.' --skip-add-drop-table --skip-add-locks --skip-comments --skip-set-charset --tz-utc --host="${:LARAVEL_LOAD_HOST}" --port="${:LARAVEL_LOAD_PORT}" --user="${:LARAVEL_LOAD_USER}" --password="${:LARAVEL_LOAD_PASSWORD}" "${:LARAVEL_LOAD_DATABASE}"';
     }
 
     /**