QR code Google Authenticator

[nabbo]

### Steps to reproduce the issue
Enable plugin "Two Factor Authentication - Google Authenticator"

### Expected result
When Google Authenticator is enabled in user profile the QR Code is generated


### Actual result
QR code is not generated


### System information (as much as possible)
Joomla 3.9.4


### Additional comments
Qr code is generated in /libraries/fof/encrypt/totp.php in line 157
"$encoder = "https://chart.googleapis.com/chart?chs= ... ht=qr&chl=";"

But the QR code generation service of Google is deprecated in March 14, 2019:
https://developers.google.com/chart/infographics/

[toivo]

Ok, the plugin Two Factor Authentication - Google Authenticator generates QR codes when you start using the app.

We have a problem if the infographics service has now been turned off, but if the plugin was installed earlier, it still works all right with the Google Authenticator app, at least in Android environment.

Google has a history of deprecating free services, for example their translation app.