nginx module logs debug info as errors

[nioncode]

Most (all?) mod_opentelemetry logs use NGX_LOG_ERR severity (see e.g. https://github.com/open-telemetry/opentelemetry-cpp-contrib/blob/a02e0052e43934a9cffe23315750be03dc22dc3d/instrumentation/otel-webserver-module/src/nginx/ngx_http_opentelemetry_module.c#L671)

This is not so nice, since those are expected messages and are not created because of errors, so it seems counter intuitive to print them as errors instead of as info or debug level. It would be great if the module would only print real errors as errors, as currently our logs regularly contain false positives and we need to post-process our logs to filter those out.