logd: remove logd.both test

This test checks that kernel /dev/log* and logd do not exist and have
content in them simultaneously.  The kernel logger was removed years
ago, so that half of the test is no longer relevant.  Once that half
is removed, this test is essentially "is logd online and does it have
logs", which is already tested for in other tests, so we remove this
on entirely.

Test: logd unit tests
Change-Id: I71dff742f66fc791b7a661a363d4239363140b3f