Remove `inode/directory` mimetype from `.desktop` file
Decibels currently specifies in its .desktop
file that it can open directories, meaning you get the option to open a directory with decibels when right-clicking in nautilus.
This is cumbersome as Decibels clearly can't do that. Opening a directory using Decibels shows a "Resource not found" error.
This MR fixes the specified supported mimetypes.