Update of gimp-netpbm2gimp-plugins to Netpbm 11.04.06

This is an update of gimp-netpbm2gimp-plugins to correspond to the 26-Dec-2023 release of the Netpbm utilities. No new utilities have been added recently to Netpbm, but svgtopam had been omitted inadvertently from gimp-netpbm2gimp-plugins and is now included.

There have been a number of upstream bug fixes and feature enhancements made to various utilities. See the Netpbm change log for a list of everything that's changed in Netpbm v11.04.06 (and all prior versions in the "Advanced" release).