trampoline: prevent adding ourself on the route

Followup #10541.
Fixes tests.regtest.TestLightningSwapserver.test_swapserver_forceclose.

In the regtest bob would now signal trampoline support due to #10541 and
include Alice into the invoice trampoline as he is connected to Alice.
Alice would then try to add herself onto the trampoline route, causing
the payment to fail.

electrum/trampoline.py

@@ -224,6 +224,8 @@ def create_trampoline_route(
 ) -> LNPaymentTRoute:
     # we decide whether to convert to a legacy payment
     is_legacy, invoice_trampolines = is_legacy_relay(invoice_features, r_tags)
+    # we can be in the invoice_trampolines e.g. if we have a direct channel with the recipient
+    invoice_trampolines.discard(my_pubkey)
     _logger.debug(f"Creating trampoline route for invoice_pubkey={invoice_pubkey.hex()}, {is_legacy=}")
 
     # we build a route of trampoline hops and extend the route list in place