[TASK] Improve type annotation for GU::setIndpEnv

This helps static code analysis in extensions.

Resolves: #97893
Releases: main, 11.5
Change-Id: Ie2eee8244438cc8d4624608ce261f5418540c672
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75144


Tested-by: core-ci <typo3@b13.com>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>

typo3/sysext/core/Classes/Utility/GeneralUtility.php

@@ -2394,10 +2394,10 @@ class GeneralUtility
     }
 
     /**
-     * This method is only for testing and should never be used outside tests-
+     * This method is only for testing and should never be used outside tests.
      *
-     * @param string $envName
-     * @param mixed $value
+     * @param non-empty-string $envName
+     * @param string|bool|array<string, string|bool|null>|null $value
      * @internal
      */
     public static function setIndpEnv($envName, $value)