Remove liblog's rate limiting

After a few years of being available, there only ended up being one
user of this, so it is clear that logd's duplicate message mechanism
is the favored solution.

The one user of this rate limiting is questionable as is, since due to
the nature of storaged, the mainloop only runs once per minute by
default as is, so there is essentially nothing to be gained by rate
limiting any further.

Test: build
Change-Id: I0610d11efda1ce8b581b939bad11ff295cb2daa6