In order to revert OBS Studio to its original state:
1. Uninstall OBS via the Add/Remove Programs dialog on your Windows Control Panel. While uninstalling, make sure the "user settings" checkbox is UNCHECKED. This is to preserve your current streaming setup and scene collections.
2. Delete the following files:
C:\Program Files (x86)\obs-studio\obs-plugins\64bit\obs-streamelements.dll
C:\Program Files (x86)\obs-studio\obs-plugins\64bit\obs-streamelements.pdb
C:\Program Files (x86)\obs-studio\obs-plugins\32bit\obs-streamelements.dll
C:\Program Files (x86)\obs-studio\obs-plugins\32bit\obs-streamelements.pdb
3. Reinstall OBS. You can get the latest version of OBS here.