Remove extra file-dialog step on web

[nikolausWest]

When you try to open an rrd file in the web viewer, it opens an intermediate file modal before opening the system file dialog. The intermediate modal both isn't styled like the rest of Rerun (makes it look super ugly) and seems like an unnecessary step from a user's point of view. On native we just open the system file dialog directly.

[jprochazk]

We can fix the style, but removing the modal requires PolyMeilex/rfd#129 (or similar fix for PolyMeilex/rfd#128)