Update WP-CLI documentation

[felipeelia]

Description of the Change

This PR updates our WP-CLI commands documentation. It was generated with this WP-CLI command using:

wp cli-command-docs elasticpress --custom-order=index,activate-feature,deactivate-feature,list-features,get-algorithm-version,set-algorithm-version --remove=delete_transient_on_int,custom_get_transient --custom-intro='The following WP-CLI commands are supported by ElasticPress:' > docs/wp-cli.md

Another PR will follow this one to make this process automatic.

Benefits

WP-CLI already relies on the DocBlock above each subcommand. Generating the documentation from it we will have both things always sync'd.

Possible Drawbacks

None. If someone wants to contribute with WP-CLI documentation specifically, it should be only a matter of updating the docblock in Command.php.

Changelog Entry

Changed: WP-CLI documentation was updated

[jeffpaul]

looks good to me!