docs: cgroup-v1/cpusets: update libcgroup project link

Update the libcgroup project link, in the cgroup v1/cpusets
documentation.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: kamalesh-babulal

Documentation/admin-guide/cgroup-v1/cpusets.rst

@@ -719,7 +719,7 @@ There are ways to query or modify cpusets:
    cat, rmdir commands from the shell, or their equivalent from C.
  - via the C library libcpuset.
  - via the C library libcgroup.
-   (http://sourceforge.net/projects/libcg/)
+   (https://github.com/libcgroup/libcgroup/)
  - via the python application cset.
    (http://code.google.com/p/cpuset/)