Revision 538000

graphics/libheif: Update to 1.6.2

From ChangeLog: https://github.com/strukturag/libheif/releases/tag/v1.6.2

 * support for HEIX images (10, 12 bit and chroma 4:2:2)
 * security limits for maximum image sizes have been increased
 * gdk pixbuf loader fixes

While here, fix pkg-descr portlint warning.

PR:     246921
Submitted by:   ltning-freebsd@anduin.net
Reviewed by:    freebsd@sebastiansteinmetz.ch (maintainer)