Update centos 7

Author: sboldyreva

docs/els-for-os/centos-7-els/README.md

@@ -9,7 +9,7 @@ To install the Endless Lifecycle Support repository on a server, you just need t
 In order to use Endless Lifecycle Support for CentOS 7, you will need to open TCP port 443 to the following destinations:
 
 * [cln.cloudlinux.com](http://cln.cloudlinux.com)
-* [repo.cloudlinux.com](http://repo.cloudlinux.com)
+* [repo.tuxcare.com](http://repo.tuxcare.com)
 * [els-rollout.cloudlinux.com](https://els-rollout.cloudlinux.com/)
 
 ## Installation of repositories