Several of them currently don't, FE:
Should be "</figure>".
There are also markup issues in some other demos linked from http://build.fluidproject.org/ that exist in separate repos, such as http://build.fluidproject.org/prefsEditors/demos/explorationTool/ - they aren't being tackled by this PR.
FLUID-5994 as one example. These should be corrected separately, since they're somewhat more complex cases.