Fix an invalid printf format string in symfony 4 test case

`%1$::` should be `%1$s::`
(`1$` means the first parameter, `s` meaning string)

Detected by static analysis

Author: TysonAndre

Test/KernelTestCase.php

@@ -38,7 +38,7 @@ abstract class KernelTestCase extends TestCase
     protected static function getKernelClass()
     {
         if (!isset($_SERVER['KERNEL_CLASS']) && !isset($_ENV['KERNEL_CLASS'])) {
-            throw new \LogicException(sprintf('You must set the KERNEL_CLASS environment variable to the fully-qualified class name of your Kernel in phpunit.xml / phpunit.xml.dist or override the %1$::createKernel() or %1$::getKernelClass() method.', static::class));
+            throw new \LogicException(sprintf('You must set the KERNEL_CLASS environment variable to the fully-qualified class name of your Kernel in phpunit.xml / phpunit.xml.dist or override the %1$s::createKernel() or %1$s::getKernelClass() method.', static::class));
         }
 
         if (!class_exists($class = $_SERVER['KERNEL_CLASS'] ?? $_ENV['KERNEL_CLASS'])) {