[test] Skip flaky test on windows.

Crashes flakily with stressopt/alwaysopt.

BUG=v8:4893
LOG=n
TBR=yangguo@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1863393002

Cr-Commit-Position: refs/heads/master@{#35321}

test/mjsunit/mjsunit.status

@@ -652,6 +652,9 @@
 
   # BUG(v8:4495).
   'es6/collections': [PASS, ['arch == ia32', FAST_VARIANTS]],
+
+  # BUG(v8:4893).
+  'regress/regress-crbug-506443': [PASS, ['no_snap', FAST_VARIANTS]],
 }],  # 'system == windows'
 
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