Bump system/kairos-agent to 2.20.4 (#1382)

Author: ci-robbot

packages/system/kairos-agent/collection.yaml

@@ -1,7 +1,7 @@
 packages:
   - name: "kairos-agent"
     category: "system"
-    version: "2.20.3"
+    version: "2.20.4"
     labels:
       github.repo: "kairos-agent"
       autobump.revdeps: "true"