[Q] How do I remove ChargerPluggedIn.ogg? topic

Hi,

I'm using the last Envi-ROM based in stock 23.0.1.A.0.167 and I would like to disable the charger plugged in notification so I tried to remove ChargerPluggedIn.ogg from /system/media/audio/ui but it says that it's an only read file and I can't do it. I'm root and I tried with RootExplorer, ES File Explorer, ADB (mv, chmod,...) but I'm not able to change the permissions neither the file nor /system folder.

Any idea?

Thanks in advance