Don't know if it's possible. If you delete one of the localizations, it might disappear, but that might not help you at all. Why would you want to hide it anyway?

Here's the answer from Intercom support: "The button for selecting languages can't be hidden, it will always appear when there is a second language added to the help center. I will raise this as a feature request to the team also." So hopefully it'll be available in the future.

It’s there even if there’s only one language to select from. The Intercom product team treats it as an expected behaviour.