Remove duplicate line

Same as the third line from the bottom in the 1.23.1 section.
Merge pull request #935 from sixfeetover/patch-1

Remove duplicate line
Reverting failed_start_at so it doesn't go back into negative numbers, see screenshot in comment at https://github.com/resque/resque/commit/a1429d83d1843e29e639c1a7d5a902070c433866
Merge pull request #942 from jonhyman/feature/failure

Reverting failed_start_at so it doesn't go back into negative numbers, s...