Update title for slash_commands.md

doc/integration/slash_commands.md

@@ -4,7 +4,7 @@ group: Integrations
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
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-# Slash Commands **(FREE)**
+# Slash commands in Mattermost and Slack **(FREE)**
 
 > - [Moved](https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/24780) to GitLab Free in 11.9.