Update TEST_MAPPING.

libbase and libziparchive both just moved out of system/core/, so I
don't think there's any value to running their tests when system/core/
changes. (I already added new TEST_MAPPING files to the two new projects.)

Test: treehugger
Change-Id: I0dd7acb525d9cca5349c55dc2724eab8d3a06afa