minor #10865 Fixing typo for .env.local file (james-srl)

This PR was submitted for the 4.2 branch but it was merged into the 4.1 branch instead (closes #10865).

Discussion
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Fixing typo for .env.local file

It was probably just a typo.

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Commits
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6ac15df Fixing typo for .env.local file

Author: javiereguiluz

configuration.rst

@@ -256,7 +256,7 @@ sensible, non-secret *default* values for all of your environment variables and
 *should* be commited to your repository.
 
 To override these variables with machine-specific or sensitive values, create a
-``env.local`` file. This file is **not committed to the shared repository** and
+``.env.local`` file. This file is **not committed to the shared repository** and
 is only stored on your machine. In fact, the ``.gitignore`` file that comes with
 Symfony prevents it from being committed.