Skip test-serialize/ParialSerializerCustomContext

Temporarily skip this test until it can be fixed.

TBR=machenbach@chromium.org

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7718
Change-Id: I04b6c47b72ed041b2b22669187b8afbcc0c05ff6
Reviewed-on: https://chromium-review.googlesource.com/1042398
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52960}

test/cctest/cctest.status

@@ -140,6 +140,9 @@
   'test-serialize/StartupSerializerTwice': [SKIP],
   'test-serialize/StartupSerializerOnceRunScript': [SKIP],
   'test-serialize/StartupSerializerTwiceRunScript': [SKIP],
+
+  # Until https://crbug.com/v8/7718 is fixed.
+  'test-serialize/PartialSerializerCustomContext': [SKIP],
 }],  # ALWAYS
 
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