Fix static analysis suppression in RouteCollector::removeNamedRoute() (#3445)

Remove static analysis suppression about using null as an array key (PHP
8.5 deprecation warning), by passing $name directly as it's a string,
whereas $route->getName() is string|null.

Author: akrabat

Slim/Routing/RouteCollector.php

@@ -185,8 +185,7 @@ public function removeNamedRoute(string $name): RouteCollectorInterface
     {
         $route = $this->getNamedRoute($name);
 
-        /** @psalm-suppress PossiblyNullArrayOffset */
-        unset($this->routesByName[$route->getName()], $this->routes[$route->getIdentifier()]);
+        unset($this->routesByName[$name], $this->routes[$route->getIdentifier()]);
         return $this;
     }