reverted default subtype example to VIRL V1.2.x

create-arista-veos-image/dynamic-subtype-vEOS.json

-{
-  "dynamic-subtypes": [
-    {
-      "plugin_base": "generic",
-      "device_type": "switch",
-      "plugin_desc": "Arista vEOS",
-      "cli_protocol": "ssh",
-      "plugin_name": "vEOS",
-      "cli_serial": 1,
-      "interface_range": 22,
-      "gui_visible": true,
-      "interface_pattern": "Ethernet{0}",
-      "baseline_image": "vEOS",
-      "config_disk_type": "disk",
-      "hw_ram": 2048,
-      "hw_vm_extra": "",
-      "gui_icon": "iosvl2",
-      "config_file": "/veos_config.txt",
-      "interface_first": 1,
-      "deprecated_use": "",
-      "baseline_flavor": "vEOS.medium",
-      "interface_management": "Management1"
-    }
-  ]
-}