qa: rephrase exception message

Signed-off-by: Maximilian Bösing <[email protected]>

test/Service/ConfigProviderIntegrationTest.php

@@ -78,7 +78,7 @@ public function servicesProvidedByConfigProvider(): Generator
     private static function assertMappedWithStrings(mixed $iterable): void
     {
         if (! is_array($iterable)) {
-            throw new InvalidArgumentException('Expecting value to be iterable.');
+            throw new InvalidArgumentException('Expecting value to be an array.');
         }
 
         foreach (array_keys($iterable) as $value) {