minor #18521 Fix comma space (alamirault)

This PR was merged into the 5.4 branch.

Discussion
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Fix comma space

It's minor, but while reviewing #18500 (6.2), I saw a missing space after comma

I checked all occurrences with `[a-zA-Z],[a-zA-Z]`, it's the only mistake on branch 5.4

Commits
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3114363 Fix comma space

Author: javiereguiluz

http_client.rst

@@ -1534,7 +1534,7 @@ that requires HTTPlug dependencies::
     }
 
 Because :class:`Symfony\\Component\\HttpClient\\HttplugClient` implements the
-three interfaces,you can use it this way::
+three interfaces, you can use it this way::
 
     use Symfony\Component\HttpClient\HttplugClient;