There is not a "Delete Duplicates" command that I know of. However, it is easily accomplished by using the SelDup (Select Duplicates) command, then just deleting the selection. If you want, you can string together the commands in a button, or alias:
! _SelDup _Delete
Keep in mind that SelDup selects exact duplicates. If you have 2 lines on top of each other, but they were created in different directions, they are not really exact, so they will not be selected. If you want to delete similar objects as opposed to exact duplicates, there is a plug-in that can do this. If you are interested, I will do some digging and find a link for you.