Skip computed property name test on Windows

BUG=v8:3815
LOG=N
TBR=dslomov@chromium.org

Review URL: https://codereview.chromium.org/854903002

Cr-Commit-Position: refs/heads/master@{#26085}

test/mjsunit/mjsunit.status

@@ -514,7 +514,7 @@
   'debug-script-breakpoints': [PASS, FAIL],
 
   # BUG(v8:3815). TODO(arv): Investigate.
-  'harmony/computed-property-names': [PASS, FAIL]
+  'harmony/computed-property-names': [SKIP]
 }],  # 'system == windows'
 
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