Don't show translated "Content" and "Hide" and "Show" strings on untranslatable pages

[scootergrisen]

On pages like https://supertuxkart.net/Making_challenges the main content of the page is not translatable.

But strings like "Content" and "Hide" and "Show" are.

I don't like that the page switches between one language and the next line is a second language and the next line is back to the first language.

If we could exclude translation of "Content" and "Hide" and "Show" on the pages that it's not possible for translations to translate i think that would be better.

So all the main content of the page (in the grey area) is untranslated english text.
And the top and bottom of the page (in the dark area) is translated text. Which is fine.

"Hide" and "Show" is part of the Download page so it's not that is have to be removed.