ci: match renamed libzmq leak frame in lsan suppressions

- LSan symbolizes the leak as the C++ method `zmq::msg_t::init_size`
  in the Debug sanitizer build, no longer the C wrapper
  `zmq_msg_init_size`
- substring match failed (`_` vs `::`), so the suppression no longer
  applied and the asan+lsan+ubsan job failed in Pair/PubSub/Poller tests
- add the demangled frame, keep the old pattern for older libzmq

test/leak_sanitizer_suppressions.txt

@@ -1 +1,2 @@
 leak:zmq_msg_init_size
+leak:zmq::msg_t::init_size