[wpinet] Fix uv_tcp_keepalive to take seconds (#8639)

[Libuv docs](https://docs.libuv.org/en/v1.x/tcp.html) states:

> Enable / disable TCP keep-alive. delay is the initial delay in
seconds, ignored when enable is zero.

But we used std::milli, leading to being off by a factor of 1000.

wpinet/src/main/native/include/wpi/net/uv/Tcp.hpp

@@ -27,7 +27,7 @@ class Tcp final : public NetworkStreamImpl<Tcp, uv_tcp_t> {
   struct private_init {};
 
  public:
-  using Time = std::chrono::duration<uint64_t, std::milli>;
+  using Time = std::chrono::seconds;
 
   explicit Tcp(const private_init&) {}
   ~Tcp() noexcept override = default;