MST language updated

[atovpeko]

[github-actions[bot]]

Allow 10 minutes from last push for the staging site to build. If the link doesn't work, try using incognito mode instead. For internal reviewers, check web-documentation repo actions for staging build status. Link to build for this PR: http://docs-dev.timescale.com/docs-3378-docs-rfcupdate-the-mst-language-to-correctly-reflect-what-mst-is