Adjust function definition in tcp_hpts.c to avoid clang 15 warning

With clang 15, the following -Werror warning is produced:

sys/netinet/tcp_hpts.c:1594:23: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
tcp_choose_hpts_to_run()
                      ^
                       void

This is because tcp_choose_hpts_to_run() is declared with a (void)
argument list, but defined with an empty argument list. Make the
definition match the declaration.

MFC after: 3 days

(cherry picked from commit db6b32867d6ed996f8a9aad41ca6ffbaa2088e59)