Grab the central connection name from the config in harden test

Other tests grab the central connection from the config instead of hardcoding 'central'. Doing the same in 'harden prevents tenants from using the database of another tenant' for consistency.

Author: lukinovec

tests/Bootstrappers/DatabaseTenancyBootstrapperTest.php

@@ -115,7 +115,7 @@
         expect(fn () => tenancy()->initialize($tenant))->toThrow(RuntimeException::class);
 
         // Connection should be reverted back to central
-        expect(DB::connection()->getName())->toBe('central');
+        expect(DB::connection()->getName())->toBe(config('tenancy.database.central_connection'));
     } else {
         expect(fn() => tenancy()->initialize($tenant))->not()->toThrow(Throwable::class);