The previous value (0) was a special case in the fog shader.
It made the shader use the Camera's `far` value as the fog depth end
value, which led to an inconsistency in the fog rendering between
the editor and a running project. This is because the editor camera
uses a `far` property of 500 by default, whereas the Camera node's
`far` property is set to 100 by default.
The new fixed value is equal to the default `far` property in Camera,
which leads to a consistent appearance between the editor and a running
project.
This closes#31686.
bc1b2b96e1