Fix unit test failure caused by the latest community change

- global DSCP_TO_TC_MAP

Signed-off-by: Stephen Sun <[email protected]>

Author: stephenxs

device/mellanox/x86_64-mlnx_msn4600c-r0/Mellanox-SN4600C-C64/qos.json.j2

@@ -99,6 +99,10 @@
         }
     },
 {%- endmacro %}
+{%- macro generate_global_dscp_to_tc_map() %}
+{# This is an empty macro since the global DSCP_TO_TC map is not required #}
+{%- endmacro %}
+
 {% endif %}
 
 {%- include 'qos_config.j2' %}