WORKAROUND:
The text source is in User.xml file located here:
On older versions of Password Manager, it can be found here:
C:\Program Files\One Identity Password Manager\Web\User\App_Data\LocalizationStorage\en-US
On Password Manager 5.15 and newer versions, it can be found here:
C:\Program Files\One Identity\Password Manager\Web\SelfService\assets\i18n\en-US.json
The text is in the section "Action.AuthenticationWithRadius.PageTip"
Modify the text as desired, save the file, and restart IIS for the changes to take effect.