chore: add syntax highlighting

src/install/npm/snmp/podman-us.mdx

@@ -196,7 +196,7 @@ headingText: SNMP security prerequisites
 <Callout variant="tip">
   The default trap listening port for **ktranslate** is port `1620 (TCP/UDP)`. To use the more common trap port of `162`, you will need to set an `iptables` pre-routing rule on the container host with the command:
 
-  ```
+  ```shell
   sudo iptables -t nat -A PREROUTING -p udp --dport 162 -j REDIRECT --to-port 1620
   ```