Fix testUnlinkSlide using same slide for both lookups

findIriBy with identical criteria returned the same slide for both
$slideUlid1 and $slideUlid2, so the PUT created only one relation.
The first DELETE succeeded but the second failed with "Relation not
found". Use distinct slide titles to get two different slides.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: turegjorup

tests/Api/PlaylistSlideTest.php

@@ -158,9 +158,9 @@ public function testUnlinkSlide(): void
         $iri = $this->findIriBy(Playlist::class, ['tenant' => $this->tenant]);
         $playlistUlid = $this->iriHelperUtils->getUlidFromIRI($iri);
 
-        $iri = $this->findIriBy(Slide::class, ['tenant' => $this->tenant]);
+        $iri = $this->findIriBy(Slide::class, ['tenant' => $this->tenant, 'title' => 'slide_abc_2']);
         $slideUlid1 = $this->iriHelperUtils->getUlidFromIRI($iri);
-        $iri = $this->findIriBy(Slide::class, ['tenant' => $this->tenant]);
+        $iri = $this->findIriBy(Slide::class, ['tenant' => $this->tenant, 'title' => 'slide_abc_3']);
         $slideUlid2 = $this->iriHelperUtils->getUlidFromIRI($iri);
 
         // First create relations to ensure they exist before deleting theme.