https: Remove validation
https: Remove validation

https.Server will return an error if the configuration is not correct.

Validate() is useful in the Prometheus server because we want to fail before opening
the TSDB if the configuration is not correct. For Pushgateway, let's use
the simple path.

Signed-off-by: Julien Pivotto <df1ed88a312a603dfee9f157a90fa8f7f195ab59@inuits.eu>

prometheus/pushgateway,prometheus/pushgateway,prometheus/pushgateway