Convert all remaining json manifests to yaml

This conversion can be validated using this script:

 #!/bin/bash

mkdir -p repo && cd repo && ostree init --repo . --mode=archive && cd ..
variants=('silverblue' 'kinoite' 'xfce' 'lxqt')

for v in ${variants[@]}; do
    sudo rpm-ostree compose tree --repo=repo --print-only fedora-$v.yaml > $v.yaml.out
done

git checkout --quiet HEAD~
for v in ${variants[@]}; do
    sudo rpm-ostree compose tree --repo=repo --print-only fedora-$v.yaml > $v.json.out
done

for v in ${variants[@]}; do
    if [[ ! -z $(diff $v.json.out $v.yaml.out) ]]; then
        echo ""
        echo "$v: JSON != YAML"
        diff $v.json.out $v.yaml.out
        echo ""
        has_diff="true"
    fi
done

git checkout --quiet master
rm -rf ./repo
for v in ${variants[@]}; do
    rm ./$v.json.out ./$v.yaml.out
done

if [[ $has_diff == "true" ]]; then
    echo "Found some diff!"
else
    echo "OK!"
fi

fedora-silverblue.yaml

@@ -1,4 +1,4 @@
-include: gnome-desktop-pkgs.json
+include: gnome-desktop-pkgs.yaml
 ref: fedora/rawhide/${basearch}/silverblue
 rojig:
   name: fedora-silverblue
@@ -11,7 +11,7 @@ packages:
   # Does it really still make sense to ship Qt by default if we
   # expect people to run apps in containers?
   - qgnomeplatform
-  # hfs filesystem tools for Apple hardware
+  # HFS filesystem tools for Apple hardware
   # See https://github.com/projectatomic/rpm-ostree/issues/1380
   - hfsplus-tools
   # Bundle the minimal -devel packages needed to build a kernel.