Changing the `logger-path` doesn't seem to completely work

[flori]

If I enable verbose output for the prometheus_exporter executable and try to log to stdout, parts of the log output still go to stderr even though the log lines aren't reporting any errors, see:

 prometheus_exporter master #e763dc6 ⮑ 0 $ prometheus_exporter -v --logger-path=/dev/stdout >/dev/null
[2023-11-29 11:51:56] INFO  WEBrick 1.8.1
[2023-11-29 11:51:56] INFO  ruby 3.2.2 (2023-03-30) [arm64-darwin22]
[2023-11-29 11:51:56] INFO  WEBrick::HTTPServer#start: pid=92385 port=9394

This also applies to any requests that are processed including successful ones.