minor #9568 Document the DotEnv::overload() method (fmata, javiereguiluz)

This PR was merged into the master branch.

Discussion
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Document the DotEnv::overload() method

I'm not sure how to update the doc according my PR symfony/symfony#26859 which is pending review but feel free to comment if I did a mistake. Thank you.

Commits
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38e4f08 Reword
f8a3c0d Update dotenv.rst
6325759 Update dotenv.rst
c8ad296 Update dotenv.rst

Author: javiereguiluz

components/dotenv.rst

@@ -58,9 +58,14 @@ Access the value with ``getenv()`` in your code::
     $dbUser = getenv('DB_USER');
     // you can also use ``$_ENV`` or ``$_SERVER``
 
-.. note::
+The ``load()`` method never overwrites existing environment variables. Use the
+``overload()`` method if you need to overwrite them::
+
+    // ...
+    $dotenv->overload(__DIR__.'/.env');
 
-    Symfony Dotenv never overwrites existing environment variables.
+.. versionadded:: 4.2
+    The ``Dotenv::overload()`` method was introduced in Symfony 4.2.
 
 You should never store a ``.env`` file in your code repository as it might
 contain sensitive information; create a ``.env.dist`` file with sensible