refactor: rename variable name

Author: kenjis

system/Router/RouteCollection.php

@@ -1427,8 +1427,8 @@ protected function create(string $verb, string $from, $to, ?array $options = nul
         // routes should always be the "source of truth".
         // this works only because discovered routes are added just prior
         // to attempting to route the request.
-        $fromExists = isset($this->routes[$verb][$routeKey]);
-        if ((isset($this->routesNames[$verb][$name]) || $fromExists) && ! $overwrite) {
+        $routeKeyExists = isset($this->routes[$verb][$routeKey]);
+        if ((isset($this->routesNames[$verb][$name]) || $routeKeyExists) && ! $overwrite) {
             return;
         }