opt(compressor): remove redundant function

Signed-off-by: Jiyong Huang <huangjy@emqx.io>

internal/compressor/compressor.go

@@ -18,7 +18,6 @@ import (
 	"bytes"
 	"compress/zlib"
 	"fmt"
-	"github.com/lf-edge/ekuiper/pkg/api"
 	"github.com/lf-edge/ekuiper/pkg/message"
 )
 
@@ -38,14 +37,6 @@ type zlibCompressor struct {
 	buffer bytes.Buffer
 }
 
-func (z *zlibCompressor) Close(ctx api.StreamContext) error {
-	if z.writer != nil {
-		ctx.GetLogger().Infof("closing zlib compressor")
-		return z.writer.Close()
-	}
-	return nil
-}
-
 func (z *zlibCompressor) Compress(data []byte) ([]byte, error) {
 	z.buffer.Reset()
 	z.writer.Reset(&z.buffer)