[javascriptcore-test262-automation] Updated curation log with latest revision...

[javascriptcore-test262-automation] Updated curation log with latest revision sha's from export and changed files.
    sourceRevisionAtLastExport: 8e5433b70f targetRevisionAtLastExport: 18bf7976

implementation-contributed/curation_logs/javascriptcore.json

 {
-  "sourceRevisionAtLastExport": "8e5433b70f",
-  "targetRevisionAtLastExport": "18bf7976f5",
+  "sourceRevisionAtLastExport": "51c20fe3ea",
+  "targetRevisionAtLastExport": "f8bd9710a3",
   "curatedFiles": {
     "/stress/Number-isNaN-basics.js": "DELETED_IN_TARGET",
     "/stress/Object_static_methods_Object.getOwnPropertyDescriptors-proxy.js": "DELETED_IN_TARGET",