Drop nullable $eventName parameter support on StimulusAttributes::normalizeEventName() method

Resolves suggestion #2159 (comment)

Author: 7-zete-7

src/StimulusBundle/src/Dto/StimulusAttributes.php

@@ -75,7 +75,7 @@ public function addAction(string $controllerName, string $actionName, ?string $e
         $this->actions[] = [
             'controllerName' => $controllerName,
             'actionName' => $actionName,
-            'eventName' => $this->normalizeEventName($eventName),
+            'eventName' => null !== $eventName ? $this->normalizeEventName($eventName) : null,
         ];
 
         foreach ($parameters as $name => $value) {
@@ -221,12 +221,8 @@ private function normalizeControllerName(string $controllerName): string
     /**
      * @see https://stimulus.hotwired.dev/reference/actions
      */
-    private function normalizeEventName(?string $eventName): ?string
+    private function normalizeEventName(string $eventName): string
     {
-        if (null === $eventName) {
-            return null;
-        }
-
         return preg_replace_callback('/^.+(?=:)/', fn (array $matches): string => $this->normalizeControllerName($matches[0]), $eventName);
     }