Temporarily disable failing gtests on riscv64.

Bug: 376621099
Test: launch a custom LUCI build with this CL:
    led get-builder art/ci/qemu-riscv6-ndebug | \
    led edit-gerrit-cl https://android-review.googlesource.com/c/platform/art/+/3327994 | \
    led launch
Change-Id: Ib7715e3934154f060771c1741dc418df6c50e7ee
2 files changed