minor #17210 [Security] update Voter return type (mohamedGasmii)

This PR was submitted for the 6.0 branch but it was merged into the 4.4 branch instead.

Discussion
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[Security] update Voter return type

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Commits
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f8dd322 [Security] update Voter return type

Author: xabbuh

security/voters.rst

@@ -56,8 +56,8 @@ which makes creating a voter even easier::
 
     abstract class Voter implements VoterInterface
     {
-        abstract protected function supports($attribute, $subject);
-        abstract protected function voteOnAttribute($attribute, $subject, TokenInterface $token);
+        abstract protected function supports($attribute, $subject): bool;
+        abstract protected function voteOnAttribute($attribute, $subject, TokenInterface $token): bool;
     }
 
 .. _how-to-use-the-voter-in-a-controller: