Update PHP Redlock impl. doc (#195)

Fix the PHP Redlock impl. link and move it as the 1st mentioned PHP
impl. as it is the most popular and the only library which supports both
https://github.com/phpredis/phpredis and
https://github.com/predis/predis clients.

Signed-off-by: Michael Voříšek <[email protected]>

Author: mvorisek

topics/distlock.md

@@ -28,8 +28,8 @@ already available that can be used for reference.
 * [Redlock-py](https://github.com/SPSCommerce/redlock-py) (Python implementation).
 * [Pottery](https://github.com/brainix/pottery#redlock) (Python implementation).
 * [Aioredlock](https://github.com/joanvila/aioredlock) (Asyncio Python implementation).
+* [RedisMutex](https://github.com/malkusch/lock#redismutex) (PHP implementation with both [Redis extension](https://github.com/phpredis/phpredis) and [Predis library](https://github.com/predis/predis) clients support).
 * [Redlock-php](https://github.com/ronnylt/redlock-php) (PHP implementation).
-* [PHPRedisMutex](https://github.com/malkusch/lock#phpredismutex) (further PHP implementation).
 * [cheprasov/php-redis-lock](https://github.com/cheprasov/php-redis-lock) (PHP library for locks).
 * [rtckit/react-redlock](https://github.com/rtckit/reactphp-redlock) (Async PHP implementation).
 * [Redsync](https://github.com/go-redsync/redsync) (Go implementation).