fix: read one-sided booking times as "ab" and "bis"

tests/Model/SpotTest.php

@@ -42,7 +42,7 @@ class SpotTest extends TestCase
         // Taken 09:00-13:00 leaves 00:00-09:00 (9h) and 13:00-24:00 (11h).
         $spot = $this->spot([$this->booking($this->someoneElse(), 540, 780)]);
 
-        self::assertSame('13:00–24:00', (string) $spot->suggested());
+        self::assertSame('ab 13:00', (string) $spot->suggested());
     }
 
     public function testTheSuggestedWindowIsAlwaysBookable(): void