testutil: silence clang warnings about case sensitive includes


and remove unused include

Pick-to: 6.12
Change-Id: Ibaa7c622674c8143ffdae298c8f67aa170da79b8
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
commit6f77e19415b9a2f676e2c1eea2c211e1cd4d2461
parentb8d031d5a2182628f8857f1a6a8307ca4cf6fdd2
authorTim Blechmann <tim.blechmann@qt.io>
committerTim Blechmann <tim.blechmann@qt.io>
commit timeWed, 10 Jun 2026 07:04:01 +0000