SL-10449 remove soft gamma adjustment that breaks Mac GLSL compiler

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

@@ -336,7 +336,10 @@ void main()
     if (emissive_brightness >= 1.0)	// fullbright, skip lighting calculations
     {
         color = fullbrightAtmosTransportFrag(diffuse_srgb.rgb, additive, atten);
-        color = fullbrightScaleSoftClip(color);
+        // This call breaks the Mac GLSL compiler/linker for unknown reasons (17Mar2020)
+        // The call is either a no-op or a pure (pow) gamma adjustment, depending on GPU level
+        // TODO: determine if we want to re-apply the gamma adjustment, and if so understand & fix Mac breakage
+        //color = fullbrightScaleSoftClip(color);
 
         al = diffuse_srgb.a;
     }