naughty: autonaughty a bridge crash on arch

A particular set of events in a testcase in cockpit-files is causing
this to turn up almost all the time — but only on arch.

Known issue #6531
See also cockpit-project/cockpit#20635

naughty/arch/6531-endpoint-traceback

@@ -0,0 +1,9 @@
+*TestFiles.testSorting*
+asyncio-ERROR: Exception in callback None()
+handle: <Handle cancelled>
+Traceback (most recent call last):
+*
+self.router.endpoints[self].remove(channel)
+*
+testlib.Error: FAIL: Test completed, but found unexpected journal messages:
+asyncio-ERROR: Exception in callback None()