submarine swaps: do not set attempts parameter in pay_invoice

there is no reason to handle that differently.

electrum/lnworker.py

@@ -1474,7 +1474,7 @@ class LNWallet(LNWorker):
     async def pay_invoice(
             self, invoice: str, *,
             amount_msat: int = None,
-            attempts: int = None,  # used only in unit tests (and for swaps?!)
+            attempts: int = None,  # used only in unit tests
             full_path: LNPaymentPath = None,
             channels: Optional[Sequence[Channel]] = None,
     ) -> Tuple[bool, List[HtlcLog]]:

electrum/submarine_swaps.py

@@ -835,13 +835,13 @@ class SwapManager(Logger):
             lightning_amount_sat=lightning_amount_sat)
         # initiate fee payment.
         if fee_invoice:
-            asyncio.ensure_future(self.lnworker.pay_invoice(fee_invoice, attempts=10))
+            asyncio.ensure_future(self.lnworker.pay_invoice(fee_invoice))
         # we return if we detect funding
         async def wait_for_funding(swap):
             while swap.funding_txid is None:
                 await asyncio.sleep(1)
         # initiate main payment
-        tasks = [asyncio.create_task(self.lnworker.pay_invoice(invoice, attempts=10, channels=channels)), asyncio.create_task(wait_for_funding(swap))]
+        tasks = [asyncio.create_task(self.lnworker.pay_invoice(invoice, channels=channels)), asyncio.create_task(wait_for_funding(swap))]
         await asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED)
         return swap.funding_txid