minor #36105 [FrameworkBundle] Fix deprecation message for booting a kernel twice (jschaedl)

This PR was merged into the 4.4 branch.

Discussion
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[FrameworkBundle] Fix deprecation message for booting a kernel twice

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | - <!-- prefix each issue number with "Fix #", if any -->
| License       | MIT
| Doc PR        | - <!-- required for new features -->
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 - Always add tests and ensure they pass.
 - Never break backward compatibility (see https://symfony.com/bc).
 - Bug fixes must be submitted against the lowest maintained branch where they apply
   (lowest branches are regularly merged to upper ones so they get the fixes too.)
 - Features and deprecations must be submitted against branch master.
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Commits
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a0a6243a21 Fix deprecation messages

Author: fabpot

Test/WebTestCase.php

@@ -42,7 +42,7 @@ private function doTearDown()
     protected static function createClient(array $options = [], array $server = [])
     {
         if (static::$booted) {
-            @trigger_error(sprintf('Calling "%s()" while a kernel has been booted is deprecated since Symfony 4.4 and will throw in 5.0, ensure the kernel is shut down before calling the method.', __METHOD__), E_USER_DEPRECATED);
+            @trigger_error(sprintf('Calling "%s()" while a kernel has been booted is deprecated since Symfony 4.4 and will throw an exception in 5.0, ensure the kernel is shut down before calling the method.', __METHOD__), E_USER_DEPRECATED);
         }
 
         $kernel = static::bootKernel($options);