According to the free repair guide on Autozone, that should be the bearing lock bolt on the bottom side that holds the bearing in the holder. After you remove it, the snap ring holds the halfshaft at the holder.
See excerpt below:
- Remove the right halfshaft from the transaxle as follows: 1. Remove the bear> I found a small bolt which seems to do nothing in its place...
> Passenger side half shaft, the longer one, has a bearing.
> The bearing is secured in the bearing mount with a snap ring.
> On the bottom side of the bearing mount there is a bolt,
> maybe 15mm hex head and 1/2 maybe 3/8 long, which
> screws up into the bearing mount, but it is too short to touch
> it the bearing itself. When I removed the shaft and its bearing
> and feel the place where the bolt was expected to stick out
> I could feel a deep hole, so the bolt was far, far to short to
> make any contact with the bearing...
>
> What is this bolt for? Is this some kind of grease point or what?