Fix retain cycles in RTCUIApplicationStatusObserver.

These retain cycles are theoretical since the singleton is supposed to
live for the lifetime of the application.

These measures were removed earlier when the object was turned into
a singleton in a previous CL, see

The weak self handling and unused dealloc method is mostly noise and
can make a casual reader think that the object will have a limited
life cycle, i.e. the code may initially look like something it is not,
which could possibly be less readable. On the other hand, for people
looking out for potential retain cycles, the code may be distracting
since it looks like it may be leaking.


Cr-Original-Commit-Position: refs/heads/master@{#19811}
Cr-Mirrored-Commit: 4090f380e58beb4e192691ca50643eef3aadd25d
1 file changed