Revert "Drop the APT GPG key from images that get it via the base container"

This reverts commit 7d4bce20.

image-builder/test-recipe.yaml

@@ -12,6 +12,6 @@ actions:
       - target
     mirror: {{ $mirror }}
     variant: minbase
-    keyring-package: {{ $osname }}-archive-keyring
-    keyring-file: /etc/apt/trusted.gpg.d/{{ $osname }}-archive-keyring.gpg
+    keyring-package: apertis-archive-keyring
+    keyring-file: keyring/apertis-archive-keyring.gpg
     merged-usr: true