[12.x] Fix spliceIntoPosition docblock to allow string|int values

[amirhshokri]

The spliceIntoPosition method in src/Illuminate/Console/Scheduling/ManagesFrequencies.php can accept both strings and integers as value.

Example:

framework/src/Illuminate/Console/Scheduling/ManagesFrequencies.php

Lines 576 to 582 in ce4faf1

	public function quarterly()
	{
	return $this->spliceIntoPosition(1, 0)
	->spliceIntoPosition(2, 0)
	->spliceIntoPosition(3, 1)
	->spliceIntoPosition(4, '1-12/3');
	}