Renable v8.garbage_collection_cases on all platforms but windows

On windows, we don't get thread times, so the benchmark doesn't work

R=ernstm@chromium.org,tonyg@chromium.org
BUG=416502

Review URL: https://codereview.chromium.org/796403002

Cr-Commit-Position: refs/heads/master@{#308366}

tools/perf/benchmarks/v8.py

@@ -7,7 +7,7 @@ from telemetry.web_perf import timeline_based_measurement
 from telemetry import benchmark
 
 
-@benchmark.Disabled  # crbug.com/416502
+@benchmark.Disabled('win')  # crbug.com/416502
 class V8GarbageCollectionCases(benchmark.Benchmark):
   """Measure V8 metrics on the garbage collection cases."""
   def CreatePageTest(self, options):