flatpak: propagate glib and ostree

Pantheon's sideload broke:
```
meson.build:17:0: ERROR: Could not generate cargs for flatpak:
Package ostree-1 was not found in the pkg-config search path.
Perhaps you should add the directory containing `ostree-1.pc'
to the PKG_CONFIG_PATH environment variable
Package 'ostree-1', required by 'flatpak', not found
```

https://hydra.nixos.org/build/113077888

ZHF: NixOS#80379
(cherry picked from commit 461ea02)

pkgs/development/libraries/flatpak/default.nix

@@ -137,15 +137,13 @@ stdenv.mkDerivation rec {
     bzip2
     dbus
     dconf
-    glib
     gpgme
     json-glib
     libarchive
     libcap
     libseccomp
     libsoup
     lzma
-    ostree
     polkit
     python3
     systemd
@@ -158,6 +156,12 @@ stdenv.mkDerivation rec {
     fuse
   ];
 
+  # Required by flatpak.pc
+  propagatedBuildInputs = [
+    glib
+    ostree
+  ];
+
   checkInputs = [
     valgrind
   ];