ref guide: remove policy reference (#2755)

Author: QFREEE

solr/solr-ref-guide/modules/deployment-guide/pages/collection-management.adoc

@@ -989,7 +989,7 @@ There are additionally a number of optional parameters that determine the target
 If they are not specified in the request then their values are copied from the source collection.
 The following parameters are currently supported (described in detail in the <<create,CREATE collection>> section):
 `numShards`, `replicationFactor`, `nrtReplicas`, `tlogReplicas`, `pullReplicas`,
-`shards`, `policy`, `createNodeSet`, `createNodeSet.shuffle`, `router.*`.
+`shards`, `createNodeSet`, `createNodeSet.shuffle`, `router.*`.
 
 When the reindexing process has completed the target collection is marked using
 `property.rx: "finished"`, and the source collection state is updated to become read-write.