minor symfony#20079 style: Typo in content title (sevjan)

This PR was submitted for the 7.2 branch but it was merged into the 5.4 branch instead.

Discussion
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style: Typo in content title

Commits
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eb8cf60 style: Typo in content title

testing/database.rst

@@ -89,7 +89,7 @@ the employee which gets returned by the ``Repository``, which itself gets
 returned by the ``EntityManager``. This way, no real class is involved in
 testing.
 
-Functional Testing of A Doctrine Repository
+Functional Testing of a Doctrine Repository
 -------------------------------------------
 
 In :ref:`functional tests <functional-tests>` you'll make queries to the