fixup! Add types

Remove string types to satisfy existing `ipl-html` base implementation of
`isValidEvent()`.

This commit will be squashed into the original commit later.

Author: jrauh01

library/Vspheredb/Web/Form/PerfdataConsumerForm.php

@@ -54,7 +54,7 @@ protected function assemble(): void
         $this->addButtons(isset($implementation), 'implementation');
     }
 
-    public function isValidEvent(string $event): bool
+    public function isValidEvent($event): bool
     {
         if ($event === self::ON_DELETE) {
             return true;

library/Vspheredb/Web/Form/VCenterShipMetricsForm.php

@@ -113,7 +113,7 @@ protected function addConsumerConfig($consumer): void
         }
     }
 
-    public function isValidEvent(string $event): bool
+    public function isValidEvent($event): bool
     {
         if ($event === self::ON_DELETE) {
             return true;