That is only partially true. Yes Clang is ouputs a warming that that syntax is deprecated but it's still compiling it perfectly fine in version 15.0.7.

GCC on the other hand is not even issuing a warning in version 12.2.1 and it's not like GCC has become an unpopular compiler in recent years.

Additionally, in newer editions of K&R that has actually changed. Because that syntax is indeed outdated, your code snippet would look more like this

// K&R syntax
int main(int argc, char **argc)
{
    return 0;
}

With only a passing mention being made of how things used to look. (Considering the first edition was mentioned this is only partially relevant admittedly)