in 8d1b3223, we removed some unused "#include"s, but we failed to
address all of them in "dht" subdirectory. and the unaddressed
"#include"s are identified by the iwyu workflow.
in this change, we address the leftovers.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#21291