Fix buffer template for Arista SKU. (#10663)

Why I did it
The buffer pool & profile setting in buffer template was not correct and caused the errors like the following:

ERR swss#orchagent: :- parseReference: malformed reference:[BUFFER_PROFILE|ingress_lossless_profile]. Must not be surrounded by [ ]

How I did it
Fix the buffer pool & profile setting by removing "[]".

How to verify it
Loaded image with this fix in a switch and made sure the error was not seen anymore.

device/arista/x86_64-arista_7800r3_48cq2_lc/Arista-7800R3-48CQ2-C48/buffers_defaults_t2.j2

@@ -1,4 +1,3 @@
-
 {%- set default_cable = '5m' %}
 
 {%- macro generate_port_lists(PORT_ALL) %}
@@ -19,26 +18,26 @@
     },
     "BUFFER_PROFILE": {
         "ingress_lossless_profile": {
-            "pool":"[BUFFER_POOL|ingress_lossless_pool]",
+            "pool":"ingress_lossless_pool",
             "size":"1280",
             "dynamic_th":"-2",
             "xon_offset":"2560",
             "xon":"0",
             "xoff":"66048"
         },
         "ingress_lossy_profile": {
-            "pool":"[BUFFER_POOL|ingress_lossless_pool]",
+            "pool":"ingress_lossless_pool",
             "size":"0",
             "xon_offset":"0",
             "static_th":"30535680"
         },
         "egress_lossless_profile": {
-            "pool":"[BUFFER_POOL|ingress_lossless_pool]",
+            "pool":"ingress_lossless_pool",
             "size":"0",
             "static_th":"33030144"
         },
         "egress_lossy_profile": {
-            "pool":"[BUFFER_POOL|ingress_lossless_pool]",
+            "pool":"ingress_lossless_pool",
             "size":"0",
             "dynamic_th":"-1"
         }
@@ -49,18 +48,18 @@
     "BUFFER_QUEUE": {
 {% for port in port_names.split(',') %}
         "{{ port }}|3-4": {
-            "profile" : "[BUFFER_PROFILE|ingress_lossless_profile]"
+            "profile" : "ingress_lossless_profile"
         },
 {% endfor %}
 {% for port in port_names.split(',') %}
         "{{ port }}|0-2": {
-            "profile" : "[BUFFER_PROFILE|egress_lossy_profile]"
+            "profile" : "egress_lossy_profile"
         },
 {% endfor %}
 {% for port in port_names.split(',') %}
         "{{ port }}|5-6": {
-            "profile" : "[BUFFER_PROFILE|egress_lossy_profile]"
+            "profile" : "egress_lossy_profile"
         }{% if not loop.last %},{% endif %}
 {% endfor %}   
     }
-{%- endmacro %}
+{%- endmacro %}