Update reindex.md (opensearch-project#6760)

Added dest > pipeline to the documentation

Signed-off-by: landon-l8 <[email protected]>

Author: landon-lengyel

_api-reference/document-apis/reindex.md

@@ -73,10 +73,11 @@ slice | Whether to manually or automatically slice the reindex operation so it e
 _source | Whether to reindex source fields. Specify a list of fields to reindex or true to reindex all fields. Default is true.
 id | The ID to associate with manual slicing.
 max | Maximum number of slices.
-dest | Information about the destination index. Valid values are `index`, `version_type`, and `op_type`.
+dest | Information about the destination index. Valid values are `index`, `version_type`, `op_type`, and `pipeline`.
 index | Name of the destination index.
 version_type | The indexing operation's version type. Valid values are `internal`, `external`, `external_gt` (retrieve the document if the specified version number is greater than the document’s current version), and `external_gte` (retrieve the document if the specified version number is greater or equal to than the document’s current version).
 op_type | Whether to copy over documents that are missing in the destination index. Valid values are `create` (ignore documents with the same ID from the source index) and `index` (copy everything from the source index).
+pipeline | Which ingest pipeline to utilize during the reindex.
 script | A script that OpenSearch uses to apply transformations to the data during the reindex operation.
 source | The actual script that OpenSearch runs.
 lang | The scripting language. Valid options are `painless`, `expression`, `mustache`, and `java`.