[devices]: Reverting the xoff value for Arista 7060 t0 topology (#1726)

Author: prsunny

device/arista/x86_64-arista_7060_cx32s/Arista-7060CX-32S-D48C8/buffers_defaults_t0.j2

@@ -28,7 +28,7 @@
             "size": "11213696",
             "type": "ingress",
             "mode": "dynamic",
-            "xoff": "8356608"
+            "xoff": "3855488"
         },
         "egress_lossy_pool": {
             "size": "9532224",