ART: Stop JIT in 913-heaps

To avoid any JIT interaction, stop the JIT thread pool in
test 913-heaps.

Bug: 31385354
Test: m ART_TEST_JIT=true test-art-host-run-test-913-heaps
Change-Id: I710ca0ed3736b5394863aa76aff9ea2ae7d50cb1
2 files changed