Fix limit value in Explode process plugin documentation.

The explode migrate process plugin annotation says that:

/**
 * @code
 * process:
 *   bar:
 *     plugin: explode
 *     source: foo
 *     limit: 1
 *     delimiter: /
 * @endcode
 *
 * If foo is "node/1/edit", then bar will be ['node', '1/edit']. The PHP
 * equivalent of this would be:
 *
 * @code
 *   $bar = explode('/', $foo, 1);
 * @endcode
 */

https://git.drupalcode.org/project/drupal/-/blob/10.1.x/core/modules/mig...

which is not true. To get an array of 2 elements the limit parameter should be 2

If limit is set and positive, the returned array will contain a maximum of limit elements with the last element containing the rest of string.

https://www.php.net/manual/en/function.explode.php