minor #11285 Fixed a typo (javiereguiluz)

This PR was merged into the 3.4 branch.

Discussion
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Fixed a typo

Commits
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acd93d6 Fixed a typo

Author: javiereguiluz

security/multiple_guard_authenticators.rst

@@ -71,7 +71,7 @@ This is how your security configuration can look in action:
                         'entry_point' => '',
                         'authenticators' => [
                             LoginFormAuthenticator::class,
-                            FacebookConnectAuthenticator::class'
+                            FacebookConnectAuthenticator::class,
                         ],
                     ],
                 ],