Check out this thread https://forums.elementalgame.com/419061
Edit: Looks like the XML is still there for population => production. It's just been reduced to 0.
From the CorePlayerAbilities.xml file
<PlayerAbilityType InternalName="A_Additive_ProductionPerPopulation">
<DisplayName>Base Production Per Population</DisplayName>
<Description>How much production each unit of population produces in a city.</Description>
<Icon>Icon_Level.png</Icon>
<DefaultValue>0.0</DefaultValue>
</PlayerAbilityType>