manifest: Update EDTT to latest

Update the EDTT module to:
8d7b543d4d2f2be0f78481e4e1d8d73a88024803

Including the following:
* 8d7b543 Fix some issues found during CIS Central testing
* fb426f1 Fix crash due to race when creating simulation folder

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>