sample_config_db.json needs to be compliant with Xlate and Rev Xlate test which means we can't use uppercase mac addresses due to the reverse translation test... this doesn't apply to actual config files

Author: bradh352

src/sonic-yang-models/tests/files/sample_config_db.json

@@ -146,7 +146,7 @@
                 "nat_zone": "0",
                 "loopback_action": "forward",
                 "ipv6_use_link_local_only": "disable",
-                "mac_addr": "02:AB:CD:EF:12:34"
+                "mac_addr": "02:ab:cd:ef:12:34"
             },
             "Vlan777": {},
             "Vlan111|2a04:5555:45:6709::1/64": {
@@ -1197,7 +1197,7 @@
                 "nat_zone": "1",
                 "loopback_action": "forward",
                 "ipv6_use_link_local_only": "enable",
-                "mac_addr": "12:34:56:78:90:AB"
+                "mac_addr": "12:34:56:78:90:ab"
             },
             "Ethernet112|2a04:5555:40:a709::2/126": {
                 "scope": "global",