The language used for translation keys is cached

Follow this steps to reproduce:

• Turn multilingual on and have English and French as supported languages
• Clear the browser cache
• Edit a page while English is the current language
• Open the Insert Macro wizard. The wizard title should be in English, and it is.
• Edit the same page while French is the current language
• Open the Insert Macro wizard. The wizard title should be in French, but it's not.
• Clear the browser cache
• Reload the edit page with French as current language
• Open the Insert Macro wizard. The wizard title should be in French, and it is.

So the language used for (some of the) translation keys is cached.