Increase num_retries to reduce likelihood of test flake

Flakiness was observed in this build:
https://android-build.googleplex.com/builds/pending/P35853772/qemu_generic_arm32_gicv3_test_debug/latest/view/logs/build_error.log

But most other builds do not have this issue.

Bug: 234788755
Change-Id: I4cf7d05a56eb678164bf0006bfb190442d6d4e03