Merge pull request #8100 from zmstone/0531-sync-default-from-file-to-schema

fix(emqx_schema): sync default values

apps/emqx/etc/emqx.conf

@@ -1,4 +1,3 @@
-
 listeners.tcp.default {
   bind: "0.0.0.0:1883"
   max_connections: 1024000

apps/emqx/src/emqx_schema.erl

@@ -1017,7 +1017,10 @@ fields("tcp_opts") ->
         {"buffer",
             sc(
                 bytesize(),
-                #{desc => ?DESC(fields_tcp_opts_buffer)}
+                #{
+                    desc => ?DESC(fields_tcp_opts_buffer),
+                    default => "4KB"
+                }
             )},
         {"high_watermark",
             sc(