Disabling a Package Repository:
Usually, the package repositories are located in the definition files.You can find them in the directory named /etc/yum.repos.d . In order to disable the file, modify the proper file and set the below given parameter.
enable = 0
The above parameter will keep the repository, however it will disable it until you decide to use it in future.
Removing the Repository Completely
Simply delete the above file to remove the repository completely.