Improve wording on voting example

From a beginner perspective, it is the first time in the documentation
that the term wallets is used. Other terms such as accounts or addresses
are explained in the Introduction to smart contracts.

docs/examples/voting.rst

@@ -133,7 +133,7 @@ of votes.
             // modifies `voters[msg.sender].voted`
             Voter storage delegate_ = voters[to];
 
-            // Voters cannot delegate to wallets that cannot vote.
+            // Voters cannot delegate to accounts that cannot vote.
             require(delegate_.weight >= 1);
             sender.voted = true;
             sender.delegate = to;