[whpalmer4]

Easy. Select one of the tasks linked by the dependency. Bring up the Task inspector via cmd-1. Click on the Dependencies tab (icon is two tasks with a dependency drawn between them) and you'll see a listing of all of the dependencies involving that task. Click the little white x in the grey circle at the right side of the window for the dependency you want to remove.

Another approach would be to use View->View Options to turn on display of dependents and prerequisites in the outline display. You could then edit those columns directly to add or remove the dependencies.