Various user-facing messages still refer to Tails Installer as the canonical way to install Tails

A quick git grep points to:

• config/chroot_local-includes/usr/local/bin/tails-additional-software-config
• config/chroot_local-includes/usr/local/lib/tails-boot-device-can-have-persistence
• config/chroot_local-includes/usr/local/sbin/tails-additional-software
• possibly Tails Upgrader

We should update these messages.

Feature Branch: tails.git+iuk.git:bugfix/17204-tails-installer-mentions

Related issues

• Related to #16721 (closed)
• Blocks #16711

Original created by @intrigeri on 17204 (Redmine)