Blacklist test now timing out on gcstress/target.

Started happening in the same build as:

- interpreter switch refactoring:
https://android.googlesource.com/platform/art/+/b70c999fcc3ff4d4988e0214f4d18783ff35edf7

- R8 drop:
https://android.googlesource.com/platform/prebuilts%2Fr8/+/3f5cf1c79d98d7c2c5ee1da046cd2a028eb835e9

Test: run-libcore-tests.sh
Change-Id: I50651638d8e995acd7ff58c823ea7cd784d9cf77