use command substitution for fc correction check

The check didn't work in bash v4.3.11(linux) or bash v4.3.25(osx).
Using Bash 3.2 or Zsh 5.0.6 everything worked fine.

This fixed it for me.
`$()` substitutes stdout from the subshell. I'm pretty sure we really want to deal with the exit value. Did you mean this?

    (fc -ln -1 | grep -q draft) && lines=2

I have only tested in bash 3.2, but the above syntax works correctly to execute the appropriate logic.