awslogs: remove unused eventBuffer update

We return immediately after this, so no need to update eventBuffer:

```
16:04:35 daemon/logger/awslogs/cloudwatchlogs.go:554:5: SA4006: this value of `eventBuffer` is never used (staticcheck)
16:04:35 				eventBuffer = eventBuffer[:0]
```

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/logger/awslogs/cloudwatchlogs.go

@@ -551,7 +551,6 @@ func (l *logStream) collectBatch(created chan bool) {
 			if !more {
 				// Flush event buffer and release resources
 				l.processEvent(batch, eventBuffer, eventBufferTimestamp)
-				eventBuffer = eventBuffer[:0]
 				l.publishBatch(batch)
 				batch.reset()
 				return