lang/gcc14-devel: Restore PORTEPOCH
In spite of 2f1558e22188af8a30e374c2236a9d3d134d3b21, portmgr emails
keep complaining that version number is going backward and some tools
will break. So restore PORTEPOCH.
Fixes: 2f1558e22188 lang/gcc14-devel: Remove unnecessary PORTEPOCH