DISTANCE_FOG shader doesn't compile due to unknown variable

[mockersf]

Bevy version and features

• main after Reduce aliasing and Moiré patterns in temporal shadow filtering #22400

What you did

cargo run --example atmospheric_fog

What went wrong

error: no definition in scope for identifier: `in`
    ┌─ embedded://bevy_pbr/render/pbr_functions.wgsl:798:160
    │
798 │                 shadow = bevy_pbr::shadows::fetch_directional_shadow(i, fragment_world_position_vec4, view_direction_normal, view_z, in.frag_coord.xy);
    │                                                                                                                                                                ^^ unknown identifier
    │
    = no definition in scope for identifier: `in`

[alice-i-cecile]

Cc @superdump