fix: add shebang to run_detached script

[natthan-pigoux]

Add shebang to run_detached.sh script to run subprocess without shell=True which results as a bandit security issue.

closes #8715

[fstagni]

Please check for other places where same fix might be needed, especially in the Batch System folder.

[natthan-pigoux]

Please check for other places where same fix might be needed, especially in the Batch System folder.

I've been through #8587 and #8605 . This was the only shell=True that was actually removed.

I also had a look for subprocess commands in the BatchSystem folder, and I didn't notice any other case. Simon properly left shell=True when needed.