www/netsurf: Fix build by using gdkpixbufextra
As the BROKEN message indicates netsurf needs support for xpm loading
which was moved into gdk-pixbuf-extra.
Approved by: nc (maintainer timeout)
PR: 286037
See also: e129c081e39271edac0d7b8aa174930f4317a796
MFH: 2025Q4