Remove obsolete methods from DumpstateListener implementations

Note that with the new Bugreporting API, SystemServer is the only
expected DumpstateListener implementation. Once we fully migrate Shell
app, we can remove the implementation in BugreportService as well.

BUG: 128980174
Test: bugreport from power menu, observe progress bar

Change-Id: I40d654a70bd9ceb3a29f8a0113b85616100f4ee9
Merged-In: I40d654a70bd9ceb3a29f8a0113b85616100f4ee9