minor #15120 [Testing] Fix typo in assertEmailAttachmentCount (nclsHart)

This PR was merged into the 4.4 branch.

Discussion
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[Testing] Fix typo in assertEmailAttachmentCount

The initial typo has been fixed in symfony/symfony@327a13c.

Commits
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3a10fff [Testing] Fix typo in assertEmailAttachmentCount

Author: javiereguiluz

testing/functional_tests_assertions.rst

@@ -84,7 +84,7 @@ Mailer
 - ``assertQueuedEmailCount()``
 - ``assertEmailIsQueued()``
 - ``assertEmailIsNotQueued()``
-- ``assertEmailAttachementCount()``
+- ``assertEmailAttachmentCount()``
 - ``assertEmailTextBodyContains()``
 - ``assertEmailTextBodyNotContains()``
 - ``assertEmailHtmlBodyContains()``