Delete keyring dir when we're done

It goes away when bubblewrap does, but let's be extra safe.

Change-Id: Ic7cc81081d075cdbd50ad158369327c36c3bcda1

roles/sign-artifacts/tasks/main.yaml

@@ -24,3 +24,8 @@
   command: "gpg --homedir {{ gnupg_tmpdir.path }} --armor --detach-sign {{ item.path }}"
   with_items: "{{ artifacts.files }}"
   when: artifacts.matched|bool
+
+- name: Delete keyring directory
+  file:
+    path: "{{ gnupg_tmpdir.path }}"
+    state: absent