Google has officially suspended (pun intended) the job training rich results, this is something Google did by accident in January 2021 but now it is official. Google said they "ultimately found that it wasn't useful for the ecosystem at scale."
Yesterday, Google removed the Job training structured data documentation. Google said they "initially tested this markup with a group of site owners, and ultimately found that it wasn't useful for the ecosystem at scale."
Don't worry, this does not mean the other job rich results are going away - they are not. Google said "this change doesn't affect any other features that may use Job training markup."
If you want to leave the structured data markup on your pages you can, Google said "you can leave the markup on your site so that search engines can better understand your web page." What other search engines would benefit from it? I am not sure.
Here is a screen shot of what these rich results look like:
Forum discussion at Twitter.