as was said in the bug mentioned above, you can easily solve the problem yourself by changing the navigator.languages value in the web console. this bug is not really worth fixing due to the aforementioned reason and that it doesn't actually affect your use of the browser because the message can easily be dismissed. (this bug will be closed as wontfix unless the reporter follows up)
Bug 1849815 Comment 3 Edit History
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i can reporoduce this on nightly version 118.0a1