[dhcp_relay] Enable DHCP Relay for BmcMgmtToRRouter in init_cfg (#12648)

Why I did it
DHCP relay feature needs to be enabled for BmcMgmtToRRouter by default

How I did it
Update device type list

files/build_templates/init_cfg.json.j2

@@ -43,7 +43,7 @@
                    ("swss", "enabled", false, "enabled"),
                    ("syncd", "enabled", false, "enabled"),
                    ("teamd", "enabled", false, "enabled")] %}
-{% do features.append(("dhcp_relay", "{% if not (DEVICE_METADATA is defined and DEVICE_METADATA['localhost'] is defined and DEVICE_METADATA['localhost']['type'] is defined and DEVICE_METADATA['localhost']['type'] is not in ['ToRRouter', 'EPMS', 'MgmtTsToR', 'MgmtToRRouter']) %}enabled{% else %}disabled{% endif %}", false, "enabled")) %}
+{% do features.append(("dhcp_relay", "{% if not (DEVICE_METADATA is defined and DEVICE_METADATA['localhost'] is defined and DEVICE_METADATA['localhost']['type'] is defined and DEVICE_METADATA['localhost']['type'] is not in ['ToRRouter', 'EPMS', 'MgmtTsToR', 'MgmtToRRouter', 'BmcMgmtToRRouter']) %}enabled{% else %}disabled{% endif %}", false, "enabled")) %}
 {%- if sonic_asic_platform == "vs" %}{% do features.append(("gbsyncd", "enabled", false, "enabled")) %}{% endif %}
 {%- if include_iccpd == "y" %}{% do features.append(("iccpd", "disabled", false, "enabled")) %}{% endif %}
 {%- if include_mgmt_framework == "y" %}{% do features.append(("mgmt-framework", "enabled", true, "enabled")) %}{% endif %}