[docs] Fix syntax error
Doris Writer <writer/doriswriter>
ElasticSearch Writer <writer/elasticsearchwriter>
FTP Writer <writer/ftpwriter>
- Greenplum Reader <reader/greenlumreader>
+ Greenplum Writer <writer/greenplumwriter>
HBase 1.x Writer <writer/hbase11xwriter>
HBase 1.x Writer with Phoenix <writer/hbase11xsqlwriter>
HBase 2.0 Writer with Phoenix <writer/hbase20xsqlwriter>
