Temporarily suspend checks of GC duration metrics for the Gen-CC GC.

We have observed that sometimes the GC duration (both for full-heap
and young-generation Generational CC collections) is null
(b/271112044). Temporarily suspend the corresponding checks in test
`HeapTest.GCMetrics` (part of ART gtest `art_runtime_tests`) while we
investigate.

Test: ART_USE_READ_BARRIER=true ART_USE_GENERATIONAL_CC=true \
        m test-art-host-gtest-art_runtime_tests
Bug: 271112044
Bug: 270391874
Change-Id: I8123dbe11b077c52a2859e0f2aeaf1d734ddc1ef
1 file changed