By running the following command after updating composer.json
```
composer update chillerlan/php-qrcode chillerlan/php-settings-container
```
This change fixes a deprecation warning from Preferences ->
Personal data / Authentication -> Authenticator (OTP).
```
Return type of chillerlan\Settings\SettingsContainerAbstract::jsonSerialize() should either be compatible with JsonSerializable::jsonSerialize(): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice
1. vendor/chillerlan/php-settings-container/src/SettingsContainerAbstract.php(19): ttrss_error_handler(Return type of chillerlan\Settings\SettingsContainerAbstract::jsonSerialize() should either be compatible with JsonSerializable::jsonSerialize(): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice, vendor/chillerlan/php-settings-container/src/SettingsContainerAbstract.php)
2. vendor/composer/ClassLoader.php(571): include(/usr/share/webapps/tt-rss/vendor/chillerlan/php-settings-container/src/SettingsContainerAbstract.php)
3. vendor/composer/ClassLoader.php(428): Composer\Autoload\includeFile(/usr/share/webapps/tt-rss/vendor/composer/../chillerlan/php-settings-container/src/SettingsContainerAbstract.php)
4. vendor/chillerlan/php-qrcode/src/QROptions.php(59): loadClass(chillerlan\Settings\SettingsContainerAbstract)
5. vendor/composer/ClassLoader.php(571): include(/usr/share/webapps/tt-rss/vendor/chillerlan/php-qrcode/src/QROptions.php)
6. vendor/composer/ClassLoader.php(428): Composer\Autoload\includeFile(/usr/share/webapps/tt-rss/vendor/composer/../chillerlan/php-qrcode/src/QROptions.php)
7. vendor/chillerlan/php-qrcode/src/QRCode.php(113): loadClass(chillerlan\QRCode\QROptions)
8. classes/pref/prefs.php(958): __construct()
9. classes/pref/prefs.php(469): _get_otp_qrcode_img()
10. classes/pref/prefs.php(541): index_auth_2fa()
11. backend.php(136): index_auth()
```
The issue is fixed in php-settings-container 2.1.1 [1] Here I use the
latest php-qrcode version for another PHP 8.1 fix [2].
[1] 68bc5019c8 (diff-359c7f7a6d32d9935951e1b0742eb116fb654f4a932c8d40328bb5dcab2fa111L162)
[2] https://github.com/chillerlan/php-qrcode/issues/97