Fix compilation with ncurses 6.3 by adjusting the printf format strings.

Apparently ncurses 6.3 introduced some new formatting tweaks that
broke things.

Fixes #18110

Reference to:
* https://github.com/octo/liboping/issues/62
* https://github.com/octo/liboping/pull/61
* https://salsa.debian.org/debian/liboping/-/blob/debian/debian/patches/fix_HOST_PRINTF_format_string.patch

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
(cherry picked from commit cb4d8ccb27)