minor #44330 Fix redundant type casts (fancyweb)

This PR was merged into the 5.3 branch.

Discussion
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Fix redundant type casts

| Q             | A
| ------------- | ---
| Branch?       | 5.3
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

Continuation of symfony/symfony#44274 on 5.3

Commits
-------

4243335012 Fix redundant type casts

Translator.php

@@ -455,7 +455,7 @@ protected function computeFallbackLocales(string $locale)
      */
     protected function assertValidLocale(string $locale)
     {
-        if (!preg_match('/^[a-z0-9@_\\.\\-]*$/i', (string) $locale)) {
+        if (!preg_match('/^[a-z0-9@_\\.\\-]*$/i', $locale)) {
             throw new InvalidArgumentException(sprintf('Invalid "%s" locale.', $locale));
         }
     }