Mattermost slash commands fails docs lint

Job #542997740 failed for 7af62c56:

 doc/user/project/integrations/mattermost_slash_commands.md:150:94 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]
 doc/user/project/integrations/mattermost_slash_commands.md:151:60 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]
 doc/user/project/integrations/mattermost_slash_commands.md:153:87 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]
 doc/user/project/integrations/mattermost_slash_commands.md:154:75 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]
   ✖ ERROR: 'markdownlint' failed with errors.
 => Linting prose...
 ✔ 0 errors, 0 warnings and 0 suggestions in 1385 files.
 ✖ 1 lint test(s) failed. Review the log carefully to see full listing.