better comment

internal/redis_lua/broker_history_add_stream.lua

@@ -50,9 +50,9 @@ if use_delta == "1" and top_offset ~= 1 then
 end
 
 if top_offset == 1 then
- -- If a new epoch starts, try to delete existing stream, this may be important when
- -- meta key is evicted by Redis LRU/LFU strategies. So we emulating eviction of stream key
- -- here to keep meta key and stream keys consistent.
+ -- If a new epoch starts (thus top_offset is 1), try to delete the existing stream, this may
+ -- be important when the meta key is evicted by Redis LRU/LFU strategies. So we are emulating
+ -- an eviction of stream key here.
  redis.call("del", stream_key)
  prev_message_payload = ""
 end