SL-17274 Cleanup hard-coded gbuffer atmos flag for softenlight

indra/llrender/llshadermgr.cpp

...newview/app_settings/shaders/class1/deferred/avatarF.glsl

...a/newview/app_settings/shaders/class1/deferred/bumpF.glsl

...newview/app_settings/shaders/class1/deferred/cloudsF.glsl

...p_settings/shaders/class1/deferred/diffuseAlphaMaskF.glsl

...ngs/shaders/class1/deferred/diffuseAlphaMaskIndexedF.glsl

...ngs/shaders/class1/deferred/diffuseAlphaMaskNoColorF.glsl

...ewview/app_settings/shaders/class1/deferred/diffuseF.glsl

...app_settings/shaders/class1/deferred/diffuseIndexedF.glsl

...view/app_settings/shaders/class1/deferred/highlightF.glsl

...wview/app_settings/shaders/class1/deferred/impostorF.glsl

...wview/app_settings/shaders/class1/deferred/materialF.glsl

...a/newview/app_settings/shaders/class1/deferred/moonF.glsl

indra/newview/app_settings/shaders/class1/deferred/skyF.glsl

.../newview/app_settings/shaders/class1/deferred/starsF.glsl

...ewview/app_settings/shaders/class1/deferred/sunDiscF.glsl

...ewview/app_settings/shaders/class1/deferred/terrainF.glsl

...a/newview/app_settings/shaders/class1/deferred/treeF.glsl

...iew/app_settings/shaders/class1/deferred/underWaterF.glsl

.../newview/app_settings/shaders/class1/deferred/waterF.glsl