Fix incorrect translation flash message keys

Author: JanMikes

src/Controller/CreateCollectionController.php

@@ -78,7 +78,7 @@ public function __invoke(Request $request, #[CurrentUser] User $user): Response
                 ),
             );
 
-            $this->addFlash('success', $this->translator->trans('collections.created'));
+            $this->addFlash('success', $this->translator->trans('collections.flash.created'));
 
             return $this->redirectToRoute('puzzle_library', ['playerId' => $player->playerId]);
         }

src/Controller/DeleteCollectionController.php

@@ -63,7 +63,7 @@ public function __invoke(#[CurrentUser] User $user, string $collectionId): Respo
             ),
         );
 
-        $this->addFlash('success', $this->translator->trans('collections.deleted'));
+        $this->addFlash('success', $this->translator->trans('collections.flash.deleted'));
 
         return $this->redirectToRoute('puzzle_library', ['playerId' => $player->playerId]);
     }