chore: fix some small issues detected by golangci-lint

But not using it as some linters are either plain incorrect (the one
suggesting to not use nil for `c.t.Context()`) or just
debatable (checking for err value is a good practice, but there are
good reasons to opt out in some cases).

inlet/flow/decoder/sflow/root.go

@@ -117,7 +117,7 @@ func (nd *Decoder) Decode(in decoder.RawFlow) []*decoder.FlowMessage {
 		}
 	}
 
-	flowMessageSet, err := producer.ProcessMessageSFlow(msgDec)
+	flowMessageSet, _ := producer.ProcessMessageSFlow(msgDec)
 	for _, fmsg := range flowMessageSet {
 		fmsg.TimeReceived = ts
 		fmsg.TimeFlowStart = ts