BUG HX711.select_channel - sleep time does not match comments

[dducrest]

select_channel https://github.com/gandalf15/HX711/blob/4faae5525ced1d08e51c95728f47ac0b8864c56f/HX711_Python3/hx711.py#L83-L86

I noticed that the comment says 50ms, but the time.sleep indicates 500ms. I think that this is a likely an error that will significantly slow down the rate at which multiple channels are read.

The same conflict in documentation vs implementation appears in set_gain_A