Fixed permanently redirected link

Change-Id: I7f96a1cfa3e5aa086dc2daef00b041d90cfec639
diff --git a/configuration/dhcp-relay.rst b/configuration/dhcp-relay.rst
index 0b74050..506dbe4 100644
--- a/configuration/dhcp-relay.rst
+++ b/configuration/dhcp-relay.rst
@@ -542,4 +542,4 @@
 
 Reference
 ---------
-- http://www.cisco.com/c/en/us/support/docs/security/adaptive-security-appliance-asa-software/116265-configure-product-00.html
+- https://www.cisco.com/c/en/us/support/docs/security/adaptive-security-appliance-asa-software/116265-configure-product-00.html