✅(backend) fix flaky test in user search api

Make sure the full is never John for the first user in order to make
sure we always have only 2 users (as the search is performed on both the
email and the full name).
    
Fixes #1765
    
Signed-off-by: Anto59290 <antonin59290@hotmail.com>

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to
 - ✨(backend) add documents/all endpoint with descendants #1553
 - ✅(export) add PDF regression tests #1762
 
+### Fixed 
+
+- ✅(backend) reduce flakiness on backend test #1769
+
 ## [4.3.0] - 2026-01-05
 
 ### Added