minor #21267 [Testing] fix typo (sajadtorkamani)

This PR was submitted for the 7.3 branch but it was merged into the 6.4 branch instead.

Discussion
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[Testing] fix typo

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Commits
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622c018 fix typo

Author: javiereguiluz

testing.rst

@@ -113,7 +113,7 @@ to use the Symfony Kernel to fetch a service from the dependency injection
 container.
 
 Symfony provides a :class:`Symfony\\Bundle\\FrameworkBundle\\Test\\KernelTestCase`
-class to help you creating and booting the kernel in your tests using
+class to help you create and boot the kernel in your tests using
 ``bootKernel()``::
 
     // tests/Service/NewsletterGeneratorTest.php