chore: remove mention of `is_buffer_supported` from typespec

apps/emqx_resource/include/emqx_resource.hrl

@@ -43,7 +43,6 @@
     expire_at => infinity | integer(),
     async_reply_fun => reply_fun(),
     simple_query => boolean(),
-    is_buffer_supported => boolean(),
     reply_to => reply_fun()
 }.
 -type resource_data() :: #{