SL-16369 Remove Hardware Skinning setting

indra/newview/app_settings/high_graphics.xml

indra/newview/app_settings/low_graphics.xml

indra/newview/app_settings/mid_graphics.xml

indra/newview/app_settings/settings.xml

indra/newview/app_settings/ultra_graphics.xml

indra/newview/llfloaterpreference.cpp

indra/newview/llviewercontrol.cpp

indra/newview/llviewershadermgr.cpp

indra/newview/pipeline.cpp

indra/newview/pipeline.h

.../default/xui/en/floater_preferences_graphics_advanced.xml