Update installation.md remove "`" at "Install GitLab-Elasticsearch-indexer"

doc/install/installation.md

@@ -588,7 +588,7 @@ You can specify a different Git repository by providing it as an extra parameter
 sudo -u git -H bundle exec rake "gitlab:workhorse:install[/home/git/gitlab-workhorse,https://example.com/gitlab-workhorse.git]" RAILS_ENV=production
 ```
 
-### Install GitLab-Elasticsearch-indexer`
+### Install GitLab-Elasticsearch-indexer
 
 GitLab-Elasticsearch-Indexer uses [GNU Make](https://www.gnu.org/software/make/). The
 following command-line will install GitLab-Elasticsearch-Indexer in `/home/git/gitlab-elasticsearch-indexer`