textproc/rubygem-kramdown23: fixed conflict with bin/kramdown

This fixes a regression introduced by:
75f5671a8203881810cddb4d7166c15102eba04f
0c0c1aa14947d33a2c98eb78a3e32d48ed7ba5f0
217af8968cd618690a994d535e6b6628f26dcaf0
It caused a conflict as port textproc/rubygem-kramdown installs same
binary (bin/kramdown) as textproc/rubygem-kramdown23.

PR: 263606