fix: require fails if is_file cached by opcache (#41614)

Author: Tofandel

src/Illuminate/Foundation/Bootstrap/LoadConfiguration.php

@@ -24,7 +24,7 @@ public function bootstrap(Application $app)
         // First we will see if we have a cache configuration file. If we do, we'll load
         // the configuration items from that file so that it is very quick. Otherwise
         // we will need to spin through every configuration file and load them all.
-        if (is_file($cached = $app->getCachedConfigPath())) {
+        if (file_exists($cached = $app->getCachedConfigPath())) {
             $items = require $cached;
 
             $loadedFromCache = true;