x11/yelp: Always delete by reason of new dependency by poudriere

[Tatsuki Makino]

Hello.
poudriere always deletes and rebuilds x11/yelp.

[00:01:21] [Dry Run] Deleting yelp-42.1.pkg: new dependency: www/webkit2-gtk4

This is due to a wrong LIB_DEPENDS in x11/yelp/Makefile.
www/webkit2-gtk4 needs to be corrected to libwebkit2gtk-5.0.so.

Could someone fix it? :)

Regards.