In What is syntax highlighting and how does it work? it says:
If you're curious whether a tag has a language hint, any user is capable of checking by visiting that tag's wiki page. The language hint (if any) that is currently being used for that tag will be displayed at the very bottom, below the buttons for the wiki
At what reputation level can users suggest the language hint to be used for a tag via its tag wiki?
My understanding is that those with 20K+ or moderator privileges can approve such suggestions.