Bug 33759: Fix typo 'Thankyou' in sample notices

Bug 33759: Fix typo 'Thankyou' in sample notices

This fixes the typo 'Thankyou' in some of the sample notices.

To test:
* With the sample data
* Create and run a report:
  SELECT code,content FROM letter where content LIKE "%Thankyou%";
* Verify 3 notices contain 'Thankyou'
* Apply patch
* Drop your database
* Run the web installer
* Run report again, you should no longer get any results

Signed-off-by: Alexander Wagner <alexander.wagner@desy.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 004bde79508b0248458aad4892b70bdcc9ab7f1d)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>