✨ feat: Improve portability of CasaOS healthcheck script (#15)

Replaces the hardcoded shebang `#!/bin/bash` with `#!/usr/bin/env bash` to
ensure the script can be executed on systems where the Bash binary is not
located at the default path `/bin/bash`.

casaos-healthcheck/run.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Constants
 CONFIG_FILE="/etc/casaos/gateway.ini"