[test] Skip test for ignition.

NOTRY=true
TBR=rmcilroy@chromium.org, mythria@chromium.org
BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1562463002

Cr-Commit-Position: refs/heads/master@{#33121}

test/test262/test262.status

@@ -736,6 +736,7 @@
   'language/statements/let/global-closure-get-before-initialization': [SKIP],
   'language/statements/let/global-closure-set-before-initialization': [SKIP],
   'language/statements/let/global-use-before-initialization-in-declaration-statement': [SKIP],
+  'language/statements/let/global-use-before-initialization-in-prior-statement': [SKIP],
   'language/statements/while/S12.6.2_A4_T5': [SKIP],
 
 }],  # ignition == True