drone: do not attempt to deploy pull requests

.drone.yml

@@ -97,6 +97,7 @@ steps:
   - name: api-pr
     image: plugins/docker
     settings:
+      registry: registry.itzana.me
       dockerfile: Containerfile
       context: .
     when:
@@ -106,6 +107,7 @@ steps:
   - name: frontend-pr
     image: plugins/docker
     settings:
+      registry: registry.itzana.me
       dockerfile: web/Containerfile
       context: web
     when:
@@ -115,6 +117,7 @@ steps:
   - name: validator-pr
     image: plugins/docker
     settings:
+      registry: registry.itzana.me
       dockerfile: validation/Containerfile
       context: validation
     when:
@@ -134,6 +137,6 @@ steps:
       - pull_request
 ---
 kind: signature
-hmac: 1764861f531e7123022bf8a1898445a3cfb279274f4fa44de5b4ea9757e82401
+hmac: d83f247d4e529f2454a9e67a12db3d9cbec1d5b39c85571dc137c71f1d6adafd
 
 ...