[receiver/awsfirehose] remove error logging on gzip.Reader type assertion failure due to nil value

[yiquanzhou]

Description

Fixing a bug.

We see a lot of error logs after upgrading opentelemetry-collector-contrib to 0.120.0:

Expected *gzip.Reader, got *gzip.Reader

The root cause is that the type assertion in the following code could return ok=false when r is nil. This could happen when the marshaller is instantiated and there's no value in gzipPool yet.

r, ok := u.gzipPool.Get().(*gzip.Reader)
if !ok {
  u.logger.Error(fmt.Sprintf("Expected *gzip.Reader, got %T", r))
  // Fall through and create a new *gzip.Reader (r == nil)
}

This PR removes the error log. Since we are instantiating the reader only in the line right below

r, err = gzip.NewReader(bytes.NewReader(compressedRecord))

I don't think checking the type assertion result and logging an error is really necessary.

[atoulme]

Please add a changelog

[atoulme]

LGTM