Fix broken Software Collections link (#1242)

Author: bhrutledge

source/guides/installing-using-linux-tools.rst

@@ -90,7 +90,7 @@ To install pip, wheel, and setuptools, in a parallel, non-system environment
 
    * For Redhat, see here:
      https://developers.redhat.com/products/softwarecollections/overview
-   * For CentOS, see here: https://www.softwarecollections.org/en/
+   * For CentOS, see here: https://github.com/sclorg
 
    Be aware that collections may not contain the most recent versions.