asterisk: fix missing newline in json

pkgs/servers/asterisk/update.py

···
     pass
 
 with open("versions.json", "w") as out_file:
-    out_file.write(json.dumps(out, sort_keys=True, indent=2))
+    out_file.write(json.dumps(out, sort_keys=True, indent=2) + "\n")

pkgs/servers/asterisk/versions.json

···
     "sha256": "e7d78716a0deeadf24b7d537cd24c11c2d9a096265eefc9470565c4da0fc54c7",
     "version": "18.5.1"
   }
-}
+}