Steps to reproduce:

1. Go to the address part of the donation form
2. Enter "Mustermann" in the last name field

Expected Result:
The text "Are you sure your name is Mustermann" shows up below the field

Actual result:
Nothing happens

The current code compares the entered value with the placeholder, which is now "z. B. Mustername", but even that value doesn't trigger the behavior. The code changes for T285394: Track different donation form types in matomo replicate the broken behavior by making the check function return false. See implementation notes for why.

Implementation notes
If we decide to fix the functionality, we need to pass in the pattern as a property. The previous method (accessing a translation inside the computed function) doesn't play well with our combination of composition API + Vue 2 + Vue18n.
The language items for placeholder and validation pattern should be put close to each other in the content repository's JSON file.
The fields for last name (in this case Mustername, Mustermann, Musterfrau), street address and city are checked for containing the example in the placeholder.