Don't validate language in debugMessageTemplateIsCompatible

Problem/Solution

Our tests only run in English so we don't encounter this in our CI. However some users with sites that have non-English languages might have assertions enabled in production.

In that case the language code will not be en and an exception will be thrown even if the rest of the config is correct. From a functionality point of view the langcode itself doesn't really matter.

Removing the language check removes the risk of distro users with misconfigured servers getting an exception thrown even when everything is fine.

Remaining tasks

User interface changes

API changes

Data model changes