Q: Disable iTunes Backup Encryption

Hi,

Can anyone kindly guide me on how to disable the backup encryption in iTunes ?

It's an iPhone 4s on 9.0.2 and Windows 10 on my PC with iTunes 12.3.

I had earlier opted for the option 'Encrypt iPhone backup' to this computer in iTunes.

However, I'd like to remove the encryption now but the option is disabled (attached screenshot below).

I had even deleted my previous backups, signed out of iCloud and switched off keychain in the iPhone. All in vain !

Can any of you'll kindly guide me with the same ?

Thanks in advance,

kaly