Cleanup - remove old astc from build script

scripts/bimg_encode.lua

@@ -31,8 +31,6 @@ project "bimg_encode"
 		path.join(BIMG_DIR, "3rdparty/nvtt/**.h"),
 		path.join(BIMG_DIR, "3rdparty/pvrtc/**.cpp"),
 		path.join(BIMG_DIR, "3rdparty/pvrtc/**.h"),
-		path.join(BIMG_DIR, "3rdparty/astc/**.cpp"),
-		path.join(BIMG_DIR, "3rdparty/astc/**.h"),
 		path.join(BIMG_DIR, "3rdparty/astc-encoder/source/**.cpp"),
 		path.join(BIMG_DIR, "3rdparty/astc-encoder/source/**.h"),
 		path.join(BIMG_DIR, "3rdparty/tinyexr/**.h"),