I mentioned the deprecation of entity_id for Template Sensors in this post (~ 3 weeks ago):
It’s much more difficult to find it in the release notes for 0.115.
If entity_id contains entities you can easily identify within the actual template, you can safely remove it. However, if entity_id contains entities not listed within the template, you will have to remember why you did that because now those entities must be incorporated within the template. In this particular case, simply removing entity_id is likely to negatively affect the Template Sensor.