dirstate-v2: update constant that wasn't kept in sync Despite the best efforts of the comment, this constant wasn't kept in sync when the flags were being rewritten. The fact that this doesn't actually break anything in the Rust implementation too much (which does use directories) relies on the fact that all nodes can have children and that dirstate traversal is not based on that flag, but for metadata in optimizations. However the bug could become more serious should we start encoding stronger guarantees using a combination of flags including this one.