Remove WEBGL_compressed_texture_atc, as requested by @saschanaz

Author: ShukantPal

inputfiles/idl/WebGL WEBGL_compressed_texture_atc.widl

@@ -623,10 +623,6 @@
         "url": "https://www.khronos.org/registry/webgl/extensions/WEBGL_compressed_texture_etc1/",
         "title": "WebGL WEBGL_compressed_texture_etc1"
     },
-    {
-        "url": "https://www.khronos.org/registry/webgl/extensions/WEBGL_compressed_texture_atc/",
-        "title": "WebGL WEBGL_compressed_texture_atc"
-    },
     {
         "url": "https://www.khronos.org/registry/webgl/extensions/WEBGL_debug_renderer_info/",
         "title": "WebGL WEBGL_debug_renderer_info"