Remove invalid assertion

Remove invalid assertion

The removed assertion consistently passes not because the invoked
`close` method internally throws a `TypeError` but because the `close`
method does not exist. The ES6 specification does not define a `close`
method on the GeneratorPrototype, so this test is a tautology.

BUG=None
LOG=N
R=arv

Committed: https://crrev.com/30ea62688657f4d8c69b54b0fbe393815373e341
Cr-Commit-Position: refs/heads/master@{#27567}

[mike3, 2015-03-30 18:24:07]

mike@mikepennisi.com changed reviewers:
+ arv@chromium.org

[mike3, 2015-03-31 21:58:22]

Could you please take a look?

[arv (Not doing code reviews), 2015-03-31 22:03:10]

LGTM

[arv (Not doing code reviews), 2015-03-31 23:15:16]

The CQ bit was checked by arv@chromium.org

[commit-bot: I haz the power, 2015-03-31 23:15:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1046963002/1

[commit-bot: I haz the power, 2015-03-31 23:27:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-31 23:27:06]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/1673)

[arv (Not doing code reviews), 2015-04-01 15:20:19]

The CQ bit was checked by arv@chromium.org

[commit-bot: I haz the power, 2015-04-01 15:20:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1046963002/1

[commit-bot: I haz the power, 2015-04-01 15:22:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-01 15:22:28]

Patchset 1 (id:??) landed as
https://crrev.com/30ea62688657f4d8c69b54b0fbe393815373e341
Cr-Commit-Position: refs/heads/master@{#27567}