x11/kitty: Update to 0.28.1

• cleaned up the Makefile order to make portclippy and portfmt happy
• diff_speedup.so and unicode_names.so removed from _STRIP_TARGETS and pkg-plist as they are no longer being build (from upstream)

Release changes: https://sw.kovidgoyal.net/kitty/changelog/#id1

PR: 271263
Reported by: Yonas Yanfa <yonas.yanfa@gmail.com>