Update path to Dockerfiles in dependabot.yml

.github/dependabot.yml

@@ -10,7 +10,16 @@ updates:
       - "fguillot"
 
   - package-ecosystem: "docker"
-    directory: "/"
+    directory: "/packaging/docker/alpine"
+    schedule:
+      interval: "weekly"
+    reviewers:
+      - "fguillot"
+    assignees:
+      - "fguillot"
+
+  - package-ecosystem: "docker"
+    directory: "/packaging/docker/distroless"
     schedule:
       interval: "weekly"
     reviewers: