minor #9905 Update dotenv usage (bobvandevijver, javiereguiluz)

This PR was submitted for the master branch but it was merged into the 3.4 branch instead (closes #9905).

Discussion
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Update dotenv usage

Based on the discussion in symfony/symfony#25643, I propose to remove this note. There is no downside of using dotenv in production, and it actually brings extra value when using a "simple" Linux installation, as the environments on console and web are automatically 'identical'.

Commits
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1dc95f9 Recommend to use real env vars in production
c82f04a Update dotenv usage

Author: javiereguiluz

components/dotenv.rst

@@ -69,8 +69,12 @@ You should never store a ``.env`` file in your code repository as it might
 contain sensitive information; create a ``.env.dist`` file with sensible
 defaults instead.
 
-Symfony Dotenv should only be used in development/testing/staging environments.
-For production environments, use "real" environment variables.
+.. note::
+
+    Symfony Dotenv can be used in any environment of your application:
+    development, testing, staging and even production. However, in production
+    it's recommended to configure real environment variables to avoid the
+    performance overhead of parsing the ``.env`` file for every request.
 
 As a ``.env`` file is a regular shell script, you can ``source`` it in your own
 shell scripts: