Remove dead advanced atmos code

indra/newview/app_settings/settings.xml

@@ -10775,17 +10775,6 @@
       <key>Value</key>
       <integer>0</integer>
     </map>
-  <key>RenderUseAdvancedAtmospherics</key>
-  <map>
-    <key>Comment</key>
-    <string>Use fancy precomputed atmospherics and stuff.</string>
-    <key>Persist</key>
-    <integer>1</integer>
-    <key>Type</key>
-    <string>Boolean</string>
-    <key>Value</key>
-    <integer>0</integer>
-  </map>
   <key>RenderUseTriStrips</key>
   <map>
     <key>Comment</key>

indra/newview/skins/default/xui/en/floater_preferences_graphics_advanced.xml

@@ -867,22 +867,6 @@
       function="Pref.RenderOptionUpdate" />
   </check_box>
 
-  <!--
-  <check_box
-    control_name="RenderUseAdvancedAtmospherics"
-    height="16"
-    initial_value="true"
-    label="Advanced Atmospherics"
-    layout="topleft"
-    left="480"
-    name="UseAdvancedAtmo"
-    top_delta="16"
-    width="240">
-    <check_box.commit_callback
-      function="Pref.AdvancedAtmosphericsEnable" />
-  </check_box>
-  -->
-
   <text
     type="string"
     length="1"