minor symfony#12134 Update form_login_setup.rst (ognarb)

This PR was merged into the 4.3 branch.

Discussion
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Update form_login_setup.rst

The script ask for the generation of logout, so add this information to the doc too

Commits
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a72a8ab Update form_login_setup.rst

Author: OskarStark

security/form_login_setup.rst

@@ -31,6 +31,9 @@ and your generated code may be slightly different:
 
     Choose a name for the controller class (e.g. SecurityController) [SecurityController]:
     > SecurityController
+    
+    Do you want to generate a '/logout' URL? (yes/no) [yes]:
+    > yes
 
      created: src/Security/LoginFormAuthenticator.php
      updated: config/packages/security.yaml