When on the "Standby apps" developer options screen, the Settings app
will be greyed out, indicating that its standby bucket cannot be
changed.
Manual Test 1: Go to the "Standby apps" screen in developer options and
observe that the Settings app is greyed out.
Manual Test 2: Turn off "Adaptive Battery" in Settings and then go to
the "Standby apps" screen in developer options - observe that the
Settings app is greyed out.
Bug: 132922935
Test: manual (listed above)
Change-Id: Idb29e6105024feacc270867e46156fc6a0396b01