Remove transport-nio plugin documentation (opensearch-project#9154)

Signed-off-by: Andrew Ross <[email protected]>
Signed-off-by: Eric Pugh <[email protected]>

Author: andrross

_install-and-configure/additional-plugins/index.md

@@ -32,7 +32,6 @@ There are many more plugins available in addition to those provided by the stand
 | repository-hdfs                                                                                                        | 1.0.0                      |
 | repository-s3                                                                                                          | 1.0.0                      |
 | store-smb                                                                                                              | 1.0.0                      |
-| transport-nio                                                                                                          | 1.0.0                      |
 
 ## Related articles
 

_install-and-configure/configuring-opensearch/network-settings.md

@@ -55,5 +55,4 @@ The default OpenSearch transport is provided by the `transport-netty4` module an
 
 Plugin | Description
 :---------- | :--------
-`transport-nio`    | The OpenSearch transport based on Java NIO. <br> Installation: `./bin/opensearch-plugin install transport-nio` <br> Configuration (using `opensearch.yml`): <br> `transport.type: nio-transport` <br> `http.type: nio-http-transport`
 `transport-reactor-netty4`    | The OpenSearch HTTP transport based on [Project Reactor](https://github.com/reactor/reactor-netty) and Netty 4 (**experimental**) <br> Installation: `./bin/opensearch-plugin install transport-reactor-netty4` <br> Configuration (using `opensearch.yml`): <br> `http.type: reactor-netty4` <br> `http.type: reactor-netty4-secure`