fix array keys from cached routes (#42078)

Introduced by laravel/framework#35714.
Removed the slash to match the same array key as in
src/Illuminate/Routing/RouteCollection.php:60

CompiledRouteCollection.php

@@ -252,11 +252,7 @@ public function getRoutesByMethod()
             })
             ->map(function (Collection $routes) {
                 return $routes->mapWithKeys(function (Route $route) {
-                    if ($domain = $route->getDomain()) {
-                        return [$domain.'/'.$route->uri => $route];
-                    }
-
-                    return [$route->uri => $route];
+                    return [$route->getDomain().$route->uri => $route];
                 })->all();
             })
             ->all();