http_headers doesn't work on prometheus input

[brianzer0]

Relevant telegraf.conf

[[inputs.prometheus]]
  urls = ["https://127.0.0.1:9644/metrics"]

  [inputs.prometheus.http_headers]
     Connection = "keep-alive"

Logs from Telegraf

Dec  8 22:25:57 x telegraf[869809]: 2022-12-08T22:25:57Z E! [telegraf] Error running agent: error loading config file /etc/telegraf/telegraf.d/input_.conf: plugin inputs.prometheus: line 1: configuration specified the fields ["http_headers"], but they weren't used

System info

telegraf 1.24.24, rocky linux 9

Docker

No response

Steps to reproduce

1. Try to use "http_headers" config on prometheus input

Expected behavior

Should be able to set http headers for plugin. Also doc seems to be wrong as it tells you to set "headers" which also does not work

Actual behavior

Cant set headers for prometheus plugin

Additional info

Not sure how the unused field tracking really works, but can we just add "http_headers" to the exclude case statement in config.go?

[powersj]

Headers were only recently added here d4eda21

telegraf 1.24.24

Unless you are running a nightly build this wont work

edit: 1.25.0 will go out next week with this feature.