Update README.md (#904)

Remove podcast Voices of the ElePHPant duplicate entry.

README.md

 * [PHP Town Hall](https://phptownhall.com/) - A casual PHP podcast by Ben Edmunds and Phil Sturgeon.
 * [Voices of the ElePHPant](https://voicesoftheelephpant.com/) Interviews with the people that make the PHP community special.
 * [PHP Roundtable](https://www.phproundtable.com/) - The PHP Roundtable is a casual gathering of developers discussing topics that PHP nerds care about.
-* [Voices of the ElePHPant](https://voicesoftheelephpant.com/) - Interviews with members of PHP community.
 
 ### PHP Reading
 *PHP-releated reading materials.*