Hello,

This is a followup to https://issues.guix.gnu.org/53372  fixing Piper (which uses libratbag). Python was added to the inputs to fix the build since Meson does not propagate Python (added to inputs rather than native-inputs as guix gc shows a reference to Python).

That allows Piper to build but it had a librsvg error on startup, like syncthing-gtk in https://issues.guix.gnu.org/52651  Fixed the same way here by removing librsvg from inputs since it is propagated by gtk+.

(Also simplified the input labels while I was at it, but my quick attempt at rewriting the phases with gexps didn't get far. Since I didn't find any similar examples in current packages, I left it as is for now.)

Thanks!
John