Removes max_primary_shard_size parameter (#1914)

* Removes max_primary_shard_size parameter

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>

* Added a comment on the new parameter

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>
(cherry picked from commit cb9b5a6)

_api-reference/index-apis/shrink-index.md

@@ -58,4 +58,8 @@ You can use the request body to configure some index settings for the target ind
 Field | Type | Description
 alias | Object | Sets an alias for the target index. Can have the fields `filter`, `index_routing`, `is_hidden`, `is_write_index`, `routing`, and `search_routing`. See [Index Aliases]({{site.url}}{{site.baseurl}}/api-reference/alias/#request-body).
 settings | Object | Index settings you can apply to your target index. See [Index Settings]({{site.url}}{{site.baseurl}}/api-reference/index-apis/create-index/#index-settings).
+
+{% comment %}
+The new parameter to be called max_shard_size. 
 max_primary_shard_size | Bytes | Sets the maximum size of a primary shard in the target index. For example, if this field is set to 100 GB, and the source index's primary shards total to 300 GB, then the target index has 3 primary shards of 100 GB each.
+{% endcomment %}