bodhi-pungi: use AtomicHost variant for AH things

The compose today failed with:

```
[WARNING ] [OSTREE_INSTALLER] Patterns in config do not match any variant: ^Atomic$
```

There is no Atomic variant any longer. Let's use AtomicHost instead,
which will sync it up with what is done inthe pungi-fedora repo.

roles/bodhi2/backend/templates/pungi.rpm.conf.j2

@@ -194,7 +194,7 @@ volume_id_substitutions = {
 
 # Other ostree artifacts
 image_build = {
-    '^Everything$': [
+    '^AtomicHost$': [
         {
         [% for arch in ['x86_64', 'aarch64', 'ppc64le'] %]
             'image-build': {
@@ -215,7 +215,7 @@ image_build = {
 }
 
 ostree_installer = [
-    ('^Atomic$', {
+    ('^AtomicHost$', {
         [% for arch in ['x86_64', 'aarch64', 'ppc64le'] %]
             '[[ arch ]]': {
                 "repo": [