minor symfony#12668 symfony#12661 Remove outdated service (JoppeDC)

This PR was merged into the 4.3 branch.

Discussion
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symfony#12661 Remove outdated service

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Removed outdated service. Fixes symfony#12661

#SymfonyHackday

Commits
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98229b3 symfony#12661 Remove outdated service

security/user_provider.rst

@@ -467,9 +467,8 @@ Symfony defines several services related to user providers:
 
       Select one of the following services to display its information:
       [0] security.user.provider.in_memory
-      [1] security.user.provider.in_memory.user
-      [2] security.user.provider.ldap
-      [3] security.user.provider.chain
+      [1] security.user.provider.ldap
+      [2] security.user.provider.chain
       ...
 
 Most of these services are abstract and cannot be injected in your services.