Commit d67ef35f ("clarify documentation for
net.ipv4.igmp_max_memberships") mistakenly indented a block of
documentation such that it now looks like it belongs to a specific sysctl.
Restore that block's original position.

Cc: Jeremy Eder <jeder@redhat.com>
Signed-off-by: NBenjamin Poirier <bpoirier@suse.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>