[i18n] Update Dutch translation

[Arjen de Korte]

Citeren Jan Schneider <jan at horde.org>:

> Zitat von Arjen de Korte <build+horde at de-korte.org>:
>
>> An update for the Dutch translation is available for download from
>>
>> https://drive.google.com/file/d/1dNk-cyKdOHDCJ3NaRjI2sj3_zxR4sk8Y/view?usp=sharing
>
> Is this for master or FRAMEWORK_5_2?

Oops, sorry about the confusion. It's for FRAMEWORK_5_2. If there is  
an easy way to just grab the *.po files from master, I could probably  
also update those.

Best regards, Arjen