Update the description of the rake task of index projects

doc/integration/elasticsearch.md

@@ -473,7 +473,7 @@ The following are some available Rake tasks:
 | [`sudo gitlab-rake gitlab:elastic:index`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake)                            | Enables Elasticsearch indexing and run `gitlab:elastic:create_empty_index`, `gitlab:elastic:clear_index_status`, `gitlab:elastic:index_projects`, and `gitlab:elastic:index_snippets`.                          |
 | [`sudo gitlab-rake gitlab:elastic:pause_indexing`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake)                            | Pauses Elasticsearch indexing. Changes are still tracked. Useful for cluster/index migrations. |
 | [`sudo gitlab-rake gitlab:elastic:resume_indexing`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake)                            | Resumes Elasticsearch indexing. |
-| [`sudo gitlab-rake gitlab:elastic:index_projects`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake)                   | Iterates over all projects and queues Sidekiq jobs to index them in the background.                                                                                                       |
+| [`sudo gitlab-rake gitlab:elastic:index_projects`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake)                   | Iterates over all projects, and queues Sidekiq jobs to index them in the background. It can only be used after the index is created.                                                                                                      |
 | [`sudo gitlab-rake gitlab:elastic:index_projects_status`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake)            | Determines the overall status of the indexing. It is done by counting the total number of indexed projects, dividing by a count of the total number of projects, then multiplying by 100. |
 | [`sudo gitlab-rake gitlab:elastic:clear_index_status`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake)               | Deletes all instances of IndexStatus for all projects. Note that this command results in a complete wipe of the index, and it should be used with caution.                                                                                              |
 | [`sudo gitlab-rake gitlab:elastic:create_empty_index`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/tasks/gitlab/elastic.rake) | Generates empty indexes (the default index and a separate issues index) and assigns an alias for each on the Elasticsearch side only if it doesn't already exist.                                                                                                      |