Remove redundant vectorFieldName parameter from MariaDB example

The 'embedding' value is the default for vectorFieldName parameter,
so it can be omitted to simplify the example code.

Author: devmatt000

examples/memory/mariadb.php

@@ -34,7 +34,6 @@
     connection: DriverManager::getConnection((new DsnParser())->parse($_ENV['MARIADB_URI'])),
     tableName: 'my_table_memory',
     indexName: 'my_index',
-    vectorFieldName: 'embedding',
 );
 
 // our data