minor #14884 Change error message to reflect SecurityContext deprecation. (nickbyfleet)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes #14884).

Discussion
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Change error message to reflect SecurityContext deprecation.

This PR was submitted on the symfony/Security read-only repository by @nickbyfleet and moved automatically to the main Symfony repository (closes symfony/Security#6).

Commits
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4212bda Change error message to reflect SecurityContext deprecation.

src/Symfony/Component/Security/Http/Firewall/AccessListener.php

@@ -50,7 +50,7 @@ class AccessListener implements ListenerInterface
     public function handle(GetResponseEvent $event)
     {
         if (null === $token = $this->tokenStorage->getToken()) {
-            throw new AuthenticationCredentialsNotFoundException('A Token was not found in the SecurityContext.');
+            throw new AuthenticationCredentialsNotFoundException('A Token was not found in the TokenStorage.');
         }
 
         $request = $event->getRequest();