fix update check

[cxdy]

It seems #51 didn't work correctly even though it did during my testing, something must've changed along the way there..

root@nagios-prod:~# journalctl -fu prometheus-nagios-exporter
-- Journal begins at Mon 2024-11-11 08:20:53 EST. --
Nov 11 08:35:59 nagios-prod prometheus-nagios-exporter[3656224]: ="2024-11-11T08:35:59-05:00" level=warning msg="Nagios version wasn't found, not updating `nagios_update_available_info` metric"
Nov 11 08:36:03 nagios-prod prometheus-nagios-exporter[3656224]: ="2024-11-11T08:36:03-05:00" level=info msg="Endpoint scraped and metrics updated"
Nov 11 08:37:17 nagios-prod prometheus-nagios-exporter[3656224]: ="2024-11-11T08:37:17-05:00" level=warning msg="Nagios version wasn't found, not updating `nagios_update_available_info` metric"

Will investigate further this week. Not sure if we should roll back #51 in the meantime or not.

I think it might just be logging that line regardless of if it finds a version: https://github.com/linode-obs/nagios_exporter/blob/main/nagios_exporter.go#L469-L477

[cxdy]

Cool, it still works, just logs for no reason. I goofed.