Hopefully fix PendingIntent.getActivities() documentation wtf.

The first intent is the key. No wait, last! Or was it first?

I haven't actually read the code, didn't write it, and haven't tested
its behaviour, but surely it can't be both, and last is the only one
that makes sense.

Change-Id: Ie8435981f09be618c93680fb6056afd015090161