It seems that bincrafters/stable no longer works as a source for the
libwebp Conan package (likely due to JFrog ending Bintray, see
https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/).

conanfile.txt has been updated to use the default source (ConanCenter)
instead, which also contains the libwebp package.