chore: add return type annotation to _is_payment_required in CryptoGetAccountBalanceQuery (hiero-ledger#2188)

Signed-off-by: ManmathX <manmath2006n@gmail.com>

Author: ManmathX

src/hiero_sdk_python/query/account_balance_query.py

@@ -172,7 +172,7 @@ def _get_query_response(self, response: Any) -> crypto_get_account_balance_pb2.C
         """
         return response.cryptogetAccountBalance
 
-    def _is_payment_required(self):
+    def _is_payment_required(self) -> bool:
         """
         Account balance query does not require payment.