weather/dwd: Do not expose precipitation

The precipitation value provided by the dwd service is a quantity instead of a percentage, which is what the applet/client assumes, so let's better not expose this on its current form.

Not removing the information parsing because it might still be useful in a near future. Only affects 6.1

We want to avoid bug reports or users worried after seeing these end-of-the-world precipitation numbers:

I've navigated on the dwd documentation but unfortunately I couldn't find the actual units for this (which led me to wrongly assume it was a probability percentage in the first place). Purely based on the data provided and the rest of the API, it should be 0.1l/m², but it's just a guess.