chore: Update n8n to 2.21.4

Author: github-actions[bot]

fly.toml

@@ -4,7 +4,7 @@ kill_signal = 'SIGTERM'
 kill_timeout = '2m0s'
 
 [build]
-  image = 'n8nio/n8n:2.20.11-exp.0-exp.0'
+  image = 'n8nio/n8n:2.21.4-exp.0-exp.0'
 
 [env]
   N8N_HOST = 'n8n.isakfire.com'