Add net.ipv4.ping_group_range to sysctl whitelist

Author: orimanabu

modules/nodes-containers-sysctls-about.adoc

@@ -71,6 +71,7 @@ in the safe set:
 - *_kernel.shm_rmid_forced_*
 - *_net.ipv4.ip_local_port_range_*
 - *_net.ipv4.tcp_syncookies_*
+- *_net.ipv4.ping_group_range_*
 
 All safe sysctls are enabled by default. You can use a sysctl in a pod by modifying
 the `Pod` spec.