minor #17297 [Testing] Fix typo (JarJak)

This PR was submitted for the 6.1 branch but it was merged into the 4.4 branch instead.

Discussion
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[Testing] Fix typo

"private services services"

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Commits
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3bea56b Fix typo

Author: javiereguiluz

testing.rst

@@ -272,7 +272,7 @@ the container is stored in ``self::$container``::
 
 The container in ``self::$container`` is actually a special test container.
 It gives you access to both the public services and the non-removed
-:ref:`private services <container-public>` services.
+:ref:`private services <container-public>`.
 
 .. note::