Add a note about zstd incompatibility with k-NN and security analytics (

#5014)

* Add a note about zstd incompatibility with  k-NN and security analytics plugins

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

* Capitalization

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

* Update _im-plugin/index-codecs.md

Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

* Update _im-plugin/index-codecs.md

Co-authored-by: Nathan Bower <nbower@amazon.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

---------

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Nathan Bower <nbower@amazon.com>

_im-plugin/index-codecs.md

@@ -24,6 +24,9 @@ It may be challenging to change the codec setting of an existing index (see [Cha
 * `zstd` (OpenSearch 2.9 and later) -- This codec provides significant compression comparable to the `best_compression` codec with reasonable CPU usage and improved indexing and search performance compared to the `default` codec.
 * `zstd_no_dict` (OpenSearch 2.9 and later) -- This codec is similar to `zstd` but excludes the dictionary compression feature. It provides faster indexing and search operations compared to `zstd` at the expense of a slightly larger index size.
 
+As of OpenSearch 2.10, the `zstd` and `zstd_no_dict` compression codecs cannot be used for [k-NN]({{site.url}}{{site.baseurl}}/search-plugins/knn/index/) or [Security Analytics]({{site.url}}{{site.baseurl}}/security-analytics/index/) indexes.
+{: .warning}
+
 For the `zstd` and `zstd_no_dict` codecs, you can optionally specify a compression level in the `index.codec.compression_level` setting. This setting takes integers in the [1, 6] range. A higher compression level results in a higher compression ratio (smaller storage size) with a tradeoff in speed (slower compression and decompression speeds lead to greater indexing and search latencies). 
 
 When an index segment is created, it uses the current index codec for compression. If you update the index codec, any segment created after the update will use the new compression algorithm. For specific operation considerations, see [Index codec considerations for index operations](#index-codec-considerations-for-index-operations).