Revert "Start the migration of passwords from the Keychain."

This reverts commit b312da5608ac316b7e49459c906b5a5d72332776.

This was causing failures on the Mac Asan 64 bot. See crbug.com/508227
for details.

BUG=508227,466638

Review URL: https://codereview.chromium.org/1211253015.

Cr-Commit-Position: refs/heads/master@{#337864}
17 files changed