[fix] remove mnemonic from current-account map
[fix] remove mnemonic from current-account map

current-account is duplicated in `:qr-modal` key when tapping on `share my
profile` button in the Profile screen
this removes the mnemonic from the duplicated data so that it does persist
there after user backed up his mnemonic
this was only happening until logging out/restarting the app

Signed-off-by: yenda <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@status.im>

status-im/status-react,status-im/status-react,status-im/status-react,status-im/status-react,status-im/status-react,status-im/status-react,status-im/status-react,status-im/status-react