Not possible to remove this extra jQuery call.
It comes in via the RWML Menu stack. The comments in the source code make it explicitly clear why it’s needed.
It’s there because sometimes the elements you want to translate (like a menu) aren’t immediately available for translation, as the page loads. So this is just a simple, sure-way of being able to capture those later loading things.
You could try moving the RWML Menu stack elsewhere on the page (above or below Kalendar) to see if it gives a different result.
However given that it appears the website is built with Foundations and has a really simple site structure, I’d propose putting in two RWML Wrapper stacks; one set to EN and the other to NL.
Then add two navigation bars to your website and change their links into the EN and NL translations. Put one navigation bar into your EN wrapper and the other navigation bar into your NL wrapper. Depending on which language is selected governs which navigation bar is shown in the page.
I don’t know if the navigation bar stack you are using simply reuses the same links RapidWeaver outputs or allows you to customise the text of the links shown for each language?
Upgrading to something like the Gator stack would let you change those link texts for each nav item - and fix the mobile menu compatibility problems you currently have in that website.