devel/kiwix-lib: drop unused Meson options after dd6e94a4f51a

meson.build:1:0: ERROR: Unknown options: "ctpp2-install-prefix"

https://github.com/kiwix/libkiwix/commit/92c9a47a0d63

PR: 259080
Reported by: antoine (via exp-run)
Regressed by: https://github.com/mesonbuild/meson/commit/dbf2ace6ca1c