refactor: remove unused closure parameters in DatabaseServiceProvider (#57644)

Remove unused $app parameters from closures that don't use the
application container instance. These closures only instantiate
classes without dependencies, so the container parameter is not needed.

- db.transactions singleton
- ConcurrencyErrorDetectorContract singleton
- LostConnectionDetectorContract singleton

Author: sumaiazaman

src/Illuminate/Database/DatabaseServiceProvider.php

@@ -76,15 +76,15 @@ protected function registerConnectionServices()
             return $app['db']->connection()->getSchemaBuilder();
         });
 
-        $this->app->singleton('db.transactions', function ($app) {
+        $this->app->singleton('db.transactions', function () {
             return new DatabaseTransactionsManager;
         });
 
-        $this->app->singleton(ConcurrencyErrorDetectorContract::class, function ($app) {
+        $this->app->singleton(ConcurrencyErrorDetectorContract::class, function () {
             return new ConcurrencyErrorDetector;
         });
 
-        $this->app->singleton(LostConnectionDetectorContract::class, function ($app) {
+        $this->app->singleton(LostConnectionDetectorContract::class, function () {
             return new LostConnectionDetector;
         });
     }