[ObjC ARC] Converts ios/chrome/browser/translate:external_url_eg_tests to ARC.

Automatically generated ARCMigrate commit
Notable issues:None
BUG=624363
TEST=None

Review-Url: https://codereview.chromium.org/2884073002
Cr-Commit-Position: refs/heads/master@{#472121}
2 files changed