minor symfony#61188 [HttpKernel] Update phpdoc description (alamirault)

This PR was merged into the 7.4 branch.

Discussion
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[HttpKernel] Update phpdoc description

| Q             | A
| ------------- | ---
| Branch?       | 7.4
| Bug fix?      | no
| New feature?  | no <!-- if yes, also update src/**/CHANGELOG.md -->
| Deprecations? | no <!-- if yes, also update UPGRADE-*.md and src/**/CHANGELOG.md -->
| Issues        | Fix #... <!-- prefix each issue number with "Fix #"; no need to create an issue if none exists, explain below -->
| License       | MIT

I used the same wording as `getBuildDir` method

Commits
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f8719e7 [HttpKernel] Update phpdoc description

Author: nicolas-grekas

src/Symfony/Component/HttpKernel/KernelInterface.php

@@ -113,9 +113,9 @@ public function getStartTime(): float;
     /**
      * Gets the cache directory.
      *
-     * Since Symfony 5.2, the cache directory should be used for caches that are written at runtime.
+     * This directory should be used for caches that are written at runtime.
      * For caches and artifacts that can be warmed at compile-time and deployed as read-only,
-     * use the new "build directory" returned by the {@see getBuildDir()} method.
+     * use the "build directory" returned by the {@see getBuildDir()} method.
      */
     public function getCacheDir(): string;