That’s just some random older build I used to show the screenshots. You cannot use it to test your translations, you would need to build the installer from source. One way to handle this is to open a pull request on Github as described above. For each pull request Windows installers are built you could use to test run it.
E.g. if you look at the pull request by @mfmeulenbelt at Dutch translation of the Picard Windows installer by mfmeulenbelt · Pull Request #1233 · metabrainz/picard · GitHub you will see at the bottom a list of “Checks”:
If you click on “Details” next to the one labeled continuous-integration/appveyor/pr you will see a list of Windows builds being performed. Click the topmost one (the one for Python 3.7), then on “Artifacts” and you will get a link to download the build installer. In this case it is on AppVeyor and includes the Dutch translation.
One note about testing: The NSIS installer automatically uses the language that is configured for your Windows. So you will see the Dutch interface only if your Windows is configured to be using Dutch as default language.