As of upstream's commit "Fix missing gio-unix-2.0 dep" 2500a42286 we no longer need to specify this ourselves. See https://github.com/NixOS/nixpkgs/issues/36468 for the NixOS-wide tracking of undeclared gio-unix-2.0 workarounds.
2500a42286
wrapGAppsHook uses GTK 3