test: skip TestSubscribeRelayEstablishedMidStream (#24431)

Relates to https://github.com/coder/internal/issues/1455
From that issue:
> Going to skip this test until the underlying race in chatd is fixed.
https://github.com/coder/coder/pull/24279 was a band-aid fix that I no
longer think is valuable pursuing short term. Hugo is working on a RFC
for a redesign of the system to prevent the class of race condition into
the future.

enterprise/coderd/x/chatd/chatd_test.go

@@ -1435,6 +1435,8 @@ func TestSubscribeRelayDialCanceledOnFastCompletion(t *testing.T) {
 // condition where the relay is too slow.
 func TestSubscribeRelayEstablishedMidStream(t *testing.T) {
 	t.Parallel()
+	// TODO(hugodutka): Unskip when chatd is free of race conditions.
+	t.Skip("skipped due to inherent race condition; see https://github.com/coder/internal/issues/1455")
 
 	db, ps := dbtestutil.NewDB(t)
 	workerID := uuid.New()