Fix FOG shader issue in Compatibility mode

[rothej]

Removing #ifndef DISABLE_FOG from two places to fix shader issues in Compatibility mode. Additionally, removing if (scene_data.fog_enabled) from the same, as the shader will not function properly in compatibility mode otherwise. Manually setting fog_enabled to true breaks the shader in a different way, implying that fog_enabled should not need to be true for this shader to function in compatibility mode.

• Fixes FOG writing in shaders fails with Compatibility renderer unless enabled via WorldEnvironment #94183

[Calinou]

Tested locally, it works as expected.

While testing, I found another bug: #94567

[clayjohn]

Looks great!

[akien-mga]

Thanks!